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A plug-in hybrid electric vehicle (PHEV), plug-in hybrid vehicle (PHV), or plug-in hybrid is a hybrid vehicle which utilizes rechargeable batteries, or another energy storage device, that can be restored to full charge by connecting a plug to an external electric power source (usually a normal electric wall socket). A PHEV shares the characteristics of both a conventional hybrid electric vehicle, having an electric motor and an internal combustion engine (ICE); and of an all-electric vehicle, having a plug to connect to the electrical grid. Most PHEVs on the road today are passenger cars, but there are also PHEV versions of commercial vehicles and vans, utility trucks, buses, trains, motorcycles, scooters, and military vehicles.
The cost for electricity to power plug-in hybrids for all-electric operation has been estimated at less than one quarter of the cost of gasoline in California. Compared to conventional vehicles, PHEVs reduce air pollution locally and dependence on petroleum. PHEVs may reduce greenhouse gas emissions that contribute to global warming, compared with conventional vehicles. PHEVs also eliminate the problem of range anxiety associated to all-electric vehicles, because the combustion engine works as a backup when the batteries are depleted, giving PHEVs driving range comparable to other vehicles with gasoline tanks. Plug-in hybrids use no fossil fuel during their all-electric range and produce lower greenhouse gas emissions if their batteries are charged from renewable electricity. Other benefits include improved national energy security, fewer fill-ups at the filling station, the convenience of home recharging, opportunities to provide emergency backup power in the home, and vehicle-to-grid (V2G) applications. Several countries, including the United States and several European countries, have enacted laws to facilitate the introduction of PHEVs through grants and tax credits, emissions mandates, and by financing research and development of advanced batteries and other related technologies.
Chinese battery manufacturer and automaker BYD Auto released the F3DM to the Chinese fleet market in December 2008 and began sales to the general public in Shenzhen in March 2010. General Motors began deliveries of the Chevrolet Volt in the United States in December 2010, becoming the first plug-in hybrid available for retail sales in the American market. As of January 2014[update], the number of series production highway-capable plug-in hybrids available in the market is limited to 10 models, mainly in the United States, Japan, Western European countries and China.
As of December 2013[update], about 160,000 highway-capable plug-in hybrid electric cars have been sold worldwide since December 2008. The Chevrolet Volt family, including its siblings Opel/Vauxhall Ampera, is the world's best selling plug-in hybrid with combined sales of about 70,000 units by January 2014. The Toyota Prius PHV is the second top selling plug-in hybrid over 45,000 units sold through December 2013, followed by the Mitsubishi Outlander P-HEV with over 17,800 units. As of December 2013[update], the United States is the market segment leader, with over 95,500 plug-in hybrids delivered, followed by the Netherlands with more than 24,500 units, and Japan with over 22,200 units sold through December 2013.
A plug-in hybrid's all-electric range is designated by PHEV-[miles] or PHEV[kilometers]km in which the number represents the distance the vehicle can travel on battery power alone. For example, a PHEV-20 can travel twenty miles (32 km) without using its combustion engine, so it may also be designated as a PHEV32km.
The Energy Independence and Security Act of 2007 defines a plug-in electric drive vehicle as a vehicle that:
The Institute of Electrical and Electronics Engineers (IEEE) defines PHEVs similarly, but also requires that the hybrid electric vehicle be able to drive at least ten miles (16 km) in all-electric mode (PHEV-10; PHEV16km), while consuming no gasoline or diesel fuel.
The California Air Resources Board uses the term "off-vehicle charge capable" (OVCC) to mean having the capability to charge a battery from an off-vehicle electric energy source that cannot be connected or coupled to the vehicle in any manner while the vehicle is being driven.
Other popular terms sometimes used for plug-in hybrids are "grid-connected hybrids", "Gas-Optional Hybrid Electric Vehicle" (GO-HEV) or simply "gas-optional hybrids". General Motors is calling its Chevrolet Volt series plug-in hybrid an "Extended-Range Electric Vehicle".
The Lohner-Porsche Mixte Hybrid, produced as early as 1899, was the first hybrid electric car. Early hybrids could be charged from an external source before operation. However, the term "plug-in hybrid" has come to mean a hybrid vehicle that can be charged from a standard electrical wall socket. The term itself was coined by UC Davis Professor Andrew Frank, who has been called the "father of the plug-in hybrid." The July 1969 issue of Popular Science featured an article on the General Motors XP-883 plug-in hybrid. The concept commuter vehicle housed six 12-volt lead–acid batteries in the trunk area and a transverse-mounted DC electric motor turning a front-wheel drive. The car could be plugged into a standard North American 120 volt AC outlet for recharging.
In 2003, Renault began selling the Elect'road, a plug-in series hybrid version of their popular Kangoo, in Europe. It was sold alongside Renault's "Electri'cité" electric-drive Kangoo battery electric van. The Elect'road had a 150 km (93 mi) range using a nickel-cadmium battery pack and a 500 cc (31 cu in), 16 kilowatt liquid-cooled gasoline "range-extender" engine. It powered two high voltage/high output/low volume alternators, each of which supplied up to 5.5 kW at 132 volts at 5000 rpm. The operating speed of the internal combustion engine—and therefore the output delivered by the generators—varied according to demand. The fuel tank had a capacity of 10 liters (2.6 U.S. gal; 2.2 imp gal) and was housed within the right rear wheel arch. The range extender function was activated by a switch on the dashboard. The on-board 3.5 kilowatt charger could charge a depleted battery pack to 95% charge in about four hours from a 240 volts supply. Passenger compartment heating was powered by the battery pack as well as an auxiliary coolant circuit that was supplied by the range extender engine. After selling about 500 vehicles, primarily in France, Norway and the UK, at a price of about €25,000, the Elect'road was redesigned in 2007.
In September 2004, CalCars converted a 2004 Toyota Prius into a prototype of what it called the PRIUS+. With the addition of 130 kg (300 lb) of lead–acid batteries, the PRIUS+ achieved roughly double the fuel economy of a standard Prius and could make trips of up to 15 km (9 mi) using only electric power. The vehicle, which is owned by CalCars technical lead Ron Gremban, is used in daily driving, as well as a test bed for various improvements to the system.
On July 18, 2006, Toyota announced that it "plans to develop a hybrid vehicle that will run locally on batteries charged by a household electrical outlet before switching over to a gasoline engine for longer hauls." In April 2007 Toyota said it planned to migrate to lithium-ion batteries in future hybrid models, but not in the 2009 model year Prius. Lithium-ion batteries are expected to significantly improve fuel economy, and have a higher energy-to-weight ratio, but cost more to produce, and raise safety concerns due to high operating temperatures.
On November 29, 2006, GM announced plans to introduce a production plug-in hybrid version of Saturn's Greenline Vue SUV with an all-electric range of 10 mi (16 km). The model's sale is anticipated by third quarter 2009,[dated info] and GM announced in January 2007 that contracts had been awarded to two companies to design and test lithium-ion batteries for the vehicle. GM has said that they plan on introducing plug-in and other hybrids "for the next several years".
In January 2007, GM unveiled the prototype of the Chevrolet Volt, which was expected to feature a plug-in capable, battery-dominant series hybrid architecture called E-Flex. Future E-Flex plug-in hybrid vehicles may use gasoline, diesel, or hydrogen fuel cell power to supplement the vehicle's battery. General Motors envisions an eventual progression of E-Flex vehicles from plug-in hybrids to pure electric vehicles, as battery technology improves.
On July 25, Japan's Ministry of Land, Infrastructure and Transport certified Toyota's plug-in hybrid for use on public roads, making it the first automobile to attain such approval. Toyota plans to conduct road tests to verify its all-electric range. The Prius Plug-in Hybrid was said to have an all-electric range of 13 km (8 mi).
On August 9, 2007, General Motors vice-president Robert Lutz announced that GM is on track for Chevrolet Volt road testing in 2008 and production to begin by 2010. The Volt was designed with all-electric range of 40 mi (64 km). On September 5, Quantum Technologies and Fisker Coachbuild, LLC announced the launch of a joint venture in Fisker Automotive. Fisker intended to build a US$80,000 luxury PHEV-50, the Fisker Karma, initially scheduled for late 2009.
In September 2007, Aptera Motors announced their Typ-1 two-seater. They planned to produce both an electric 2e and a plug-in series hybrid 2h with a common three-wheeled, composite body design. As of 2009, over two thousand hybrid pre-orders had been accepted and production of the hybrid configuration was expected to begin in 2010. However, the company folded in December 2011.
On October 9, 2007, Chinese manufacturer BYD Automobile Company (which is owned by China's largest mobile phone battery maker) announced that it would be introducing a production PHEV-60 sedan in China in the second half of 2008. BYD exhibited it January 2008 at the North American International Auto Show in Detroit. Based on BYD's midsize F6 sedan, it uses lithium iron phosphate (LiFeP04)-based batteries instead of lithium-ion, and can be recharged to 70% of capacity in just 10 minutes.
On December 2007 Ford delivered the first Ford Escape Plug-in Hybrid of a fleet of 20 demonstration PHEVs to Southern California Edison. As part of this demonstration program Ford also developed the first ever flexible-fuel plug-in hybrid SUV, which was delivered in June 2008. This demonstration fleet of plug-ins has been in field testing with utility company fleets in the U.S. and Canada, and during the first two years since the program began, the fleet has logged more than 75,000 miles. On August 2009 Ford delivered the first Escape Plug-in equipped with intelligent vehicle-to-grid (V2G) communications and control system technology, and Ford plans to equip all 21 plug-in hybrid Escapes with the vehicle-to-grid communications technology. Sales of the Escape PHEV are scheduled for 2012.
On March 27, the California Air Resources Board modified their regulations, requiring automobile manufacturers to produce 58,000 plug-in hybrids during 2012 through 2014. This requirement is an asked-for alternative to an earlier mandate to produce 25,000 pure zero-emissions vehicles, reducing that requirement to 5,000. On June 26, Volkswagen announced that they would be introducing production plug-ins based on the Golf compact. Volkswagen uses the term 'TwinDrive' to denote a PHEV. In September, Mazda was reported to be planning PHEVs. On September 23, Chrysler announced that they had prototyped a plug-in Jeep Wrangler and a Chrysler Town and Country mini-van, both PHEV-40s with series powertrains, and an all-electric Dodge sports car, and said that one of the three vehicles would go into production.
On October 3, the U.S. enacted the Energy Improvement and Extension Act of 2008. The legislation provided tax credits for the purchase of plug-in electric vehicles of battery capacity over 4 kilowatt-hours. The federal tax credits were extended and modified by the American Clean Energy and Security Act of 2009, but now the battery capacity must be over 5 Kwh and the credit phases out after the automaker has sold at least 200,000 vehicles in the U.S.
On December 15, 2008 BYD Auto began selling its F3DM in China, becoming the first production plug-in hybrid sold in the world, though initially was available only for corporate and government customers. Sales to the general public began in Shenzhen in March 2010, but because the F3DM nearly doubles the price of cars that run on conventional fuel, BYD expects subsidies from the local government to make the plug-in affordable to personal buyers.
A global demonstration program involving 600 Toyota Prius Plug-in pre-production test cars began in late 2009 in Japan and by mid-2010 field testing had begun in France, Germany, the United Kingdom, Canada, and the United States.
Volvo Cars, in a joint venture with Vattenfall, a Swedish energy company, began a demonstration project with two Volvo V70 Plug-in Hybrids in Göteborg, Sweden since December 2009. As reported by the test drivers, the V70 Plug-in Hybrid demonstrators have an all-electric range between 20 kilometres (12 mi) to 30 kilometres (19 mi). The test plug-in hybrids were built with a button to allow test drivers to manually choose between electricity or diesel engine power at any time. Volvo announced series production of plug-in diesel-electric hybrids as early as 2012. Volvo claimed that its plug-in hybrid could achieve 125 miles per US gallon (1.88 L/100 km; 150 mpg-imp), based on the European test cycle.
On October 2010 Lotus Engineering unveiled the Lotus CityCar at the 2010 Paris Motor Show, a plug-in series hybrid concept car designed for flex-fuel operation on ethanol, or methanol as well as regular gasoline. The lithium battery pack provides an all-electric range of 60 kilometres (37 mi), and the 1.2-liter flex-fuel engine kicks in to allow to extend the range to more than 500 kilometres (310 mi).
GM officially launched the Chevrolet Volt in the U.S. on November 30, 2010, and retail deliveries began in December 2010. Its sibling the Opel/Vauxhall Ampera was launched in Europe between late 2011 and early 2012. The first deliveries of the Fisker Karma took place in July 2011, and deliveries to retail customers began in November 2011. The Toyota Prius Plug-in Hybrid was released in Japan in January 2012, followed by the United States in February 2012. Deliveries of the Prius PHV in Europe began in late June 2012. The Ford C-Max Energi was released in the U.S. in October 2012, the Volvo V60 Plug-in Hybrid in Sweden by late 2012.
The Honda Accord Plug-in Hybrid was released in selected U.S. markets in January 2013, and the Mitsubishi Outlander P-HEV in Japan in January 2013, becoming the first SUV plug-in hybrid in the market. Deliveries of the Ford Fusion Energi began in February 2013. BYD Auto stopped production of its BYD F3DM due to low sales, and its successor, the BYD Qin, began sales in Costa Rica in November 2013, with sales in other countries in Latin America scheduled to begin in 2014. Qin deliveries began in China in mid December 2013. Deliveries to retail customers of the limited edition McLaren P1 supercar began in the UK in October 2013, and the Porsche Panamera S E-Hybrid began deliveries in the U.S. in November 2013. The first retail deliveries of the Cadillac ELR took place in the U.S. in December 2013. Other plug-in vehicles slated to the market in 2014 are the Volkswagen XL1, Porsche 918 Spyder, Audi A3 Sportback e-tron, and BMW i8
Series hybrids use an internal combustion engine (ICE) to turn a generator, which in turn supplies current to an electric motor, which then rotates the vehicle’s drive wheels. A battery or supercapacitor pack, or a combination of the two, can be used to store excess charge. Examples of series hybrids vehicles include the Chevrolet Volt, Fisker Karma, Renault Kangoo, Elect'Road, Toyota's Japan-only Coaster light-duty passenger bus, Daimler AG's hybrid Orion bus, Opel Flextreme concept car, Swissauto REX VW Polo prototype and many diesel-electric locomotives. With an appropriate balance of components this type can operate over a substantial distance with its full range of power without engaging the ICE. As is the case for other architectures, series hybrids can operate without recharging as long as there is liquid fuel in the tank.
Parallel hybrids, such as Honda's Insight, Civic, and Accord hybrids, can simultaneously transmit power to their drive wheels from two distinct sources—for example, an internal combustion engine and a battery-powered electric drive. Although most parallel hybrids incorporate an electric motor between the vehicle's engine and transmission, a parallel hybrid can also use its engine to drive one of the vehicle's axles, while its electric motor drives the other axle and/or a generator used for recharging the batteries. This type is called a road-coupled hybrid. The Audi Duo plug-in hybrid concept car is an example of this type of parallel hybrid architecture. Parallel hybrids can be programmed to use the electric motor to substitute for the ICE at lower power demands as well as to substantially increase the power available to a smaller ICE, both of which substantially increase fuel economy compared to a simple ICE vehicle.
Series-parallel hybrids have the flexibility to operate in either series or parallel mode. Hybrid powertrains currently used by Ford, Lexus, Nissan, and Toyota, which some refer to as “series-parallel with power-split,” can operate in both series and parallel mode at the same time. As of 2007, most plug-in hybrid conversions of conventional hybrids utilize this architecture. The Toyota Prius Plug-in Hybrid operates as a series-parallel hybrid.
Batteries are DC devices while grid power is AC. In order to charge the batteries, a DC charger must be utilized. The charger can be located in several locations:
On-board chargers are mounted inside the vehicle. Since the charger takes up space and adds weight, its power capacity is generally limited by practical considerations, avoiding carrying a more powerful charger that can only be fully utilized at certain locations. However, carrying the charger along with the vehicle ensures that power will be available anywhere a power connection can be found.
Off-board chargers can be as large as needed and mounted at fixed locations, like the garage or dedicated charging stations. Built with dedicated wiring, these chargers can handle much more power and charge the batteries more quickly. However, as the output of these chargers is DC, each battery system requires the output to be changed for that car. Modern charging stations have a system for identifying the voltage of the battery pack and adjusting accordingly.
Using electric motor's inverter allows the motor windings to act as the transformer coils, and the existing high-power inverter as the AC-to-DC charger. As these components are already required on the car, and are designed to handle any practical power capability, they can be used to create a very powerful form of on-board charger with zero additional weight or size. AC Propulsion uses this charging method, referred to as "reductive charging".
Regardless of its architecture, a plug-in hybrid may be capable of charge-depleting and charge-sustaining modes. Combinations of these two modes are termed blended mode or mixed-mode. These vehicles can be designed to drive for an extended range in all-electric mode, either at low speeds only or at all speeds. These modes manage the vehicle's battery discharge strategy, and their use has a direct effect on the size and type of battery required:
Charge-depleting mode allows a fully charged PHEV to operate exclusively (or depending on the vehicle, almost exclusively, except during hard acceleration) on electric power until its battery state of charge is depleted to a predetermined level, at which time the vehicle's internal combustion engine or fuel cell will be engaged. This period is the vehicle's all-electric range. This is the only mode that a battery electric vehicle can operate in, hence their limited range.
Charge-sustaining mode is used by production hybrid vehicles (HEVs) today, and combines the operation of the vehicle's two power sources in such a manner that the vehicle is operating as efficiently as possible without allowing the battery state of charge to move outside a predetermined narrow band. Over the course of a trip in a HEV the state of charge may fluctuate but will have no net change. The battery in a HEV can thus be thought of as an energy accumulator rather than a fuel storage device. Once a plug-in hybrid has exhausted its all-electric range in charge-depleting mode, it can switch into charge-sustaining mode automatically.
Mixed mode describes a trip in which a combination of the above modes are utilized. For example, a PHEV-20 Prius conversion may begin a trip with 5 miles (8 km) of low speed charge-depleting, then get onto a freeway and operate in blended mode for 20 miles (32 km), using 10 miles (16 km) worth of all-electric range at twice the fuel economy. Finally the driver might exit the freeway and drive for another 5 miles (8 km) without the internal combustion engine until the full 20 miles (32 km) of all-electric range are exhausted. At this point the vehicle can revert to a charge sustaining-mode for another 10 miles (16 km) until the final destination is reached. Such a trip would be considered a mixed mode, as multiple modes are employed in one trip. This contrasts with a charge-depleting trip which would be driven within the limits of a PHEV's all-electric range. Conversely, the portion of a trip which extends beyond the all-electric range of a PHEV would be driven primarily in charge-sustaining mode, as used by a conventional hybrid.
PHEVs typically require deeper battery charging and discharging cycles than conventional hybrids. Because the number of full cycles influences battery life, this may be less than in traditional HEVs which do not deplete their batteries as fully. However, some authors argue that PHEVs will soon become standard in the automobile industry. Design issues and trade-offs against battery life, capacity, heat dissipation, weight, costs, and safety need to be solved. Advanced battery technology is under development, promising greater energy densities by both mass and volume, and battery life expectancy is expected to increase.
The cathodes of some early 2007 lithium-ion batteries are made from lithium-cobalt metal oxide. This material is expensive, and cells made with it can release oxygen if overcharged. If the cobalt is replaced with iron phosphates, the cells will not burn or release oxygen under any charge. The price premium for early 2007 conventional hybrids is about US$5000, some US$3000 of which is for their NiMH battery packs. At early 2007 gasoline and electricity prices, that would mean a break-even point after six to ten years of operation. The conventional hybrid premium could fall to US$2000 in five years, with US$1200 or more of that being cost of lithium-ion batteries, providing for a three-year payback. The payback period may be longer for plug-in hybrids, because of their larger, more expensive batteries.
Nickel–metal hydride and lithium-ion batteries can be recycled; Toyota, for example, has a recycling program in place under which dealers are paid a US$200 credit for each battery returned. However, plug-in hybrids typically use larger battery packs than comparable conventional hybrids, and thus require more resources. Pacific Gas and Electric Company (PG&E) has suggested that utilities could purchase used batteries for backup and load leveling purposes. They state that while these used batteries may be no longer usable in vehicles, their residual capacity still has significant value. More recently, General Motors (GM) has said it has been "approached by utilities interested in using recycled Volt batteries as a power storage system, a secondary market that could bring down the cost of the Volt and other plug-in vehicles for consumers."
Lithium iron phosphate (LiFePO4) is a class of cathode materials used in lithium iron phosphate batteries that is getting attention from the auto industry. Valence Technologies produce a lithium iron manganese phosphate (LiFeMnPO4) battery with LG Chem selling lithium iron phospate (LiFePO4) batteries for the Chevy Volt and A123 produces a lithium nano-phosphate battery. The most important merit of this battery type is safety and high-power. Lithium iron phosphate batteries are one of three major types in LFP family, the other two being nano-phosphate and nano-cocrystalline-olivine.
In France, Électricité de France (EDF) and Toyota are installing charging stations for PHEVs on roads, streets and parking lots. EDF is also partnering with Elektromotive, Ltd. to install 250 new charging points over six months from October 2007 in London and elsewhere in the UK. Recharging points also can be installed for specific uses, as in taxicab stands. Project Better Place began in October 2007 and is working with Renault on development of exchangeable batteries (battery swapping).
Ultracapacitors (or "supercapacitors") are used in some plug-in hybrids, such as AFS Trinity's concept prototype, to store rapidly available energy with their high power density, in order to keep batteries within safe resistive heating limits and extend battery life. The CSIRO's UltraBattery combines a supercapacitor and a lead acid battery in a single unit, creating a hybrid car battery that lasts longer, costs less and is more powerful than current technologies used in plug-in hybrid electric vehicles (PHEVs).
The optimum battery size varies depending on whether the aim is to reduce oil consumption, running costs, or emissions, but a recent study concluded that "The best choice of PHEV battery capacity depends critically on the distance that the vehicle will be driven between charges. Our results suggest that for urban driving conditions and frequent charges every 10 miles or less, a low-capacity PHEV sized with an AER (all electric range) of about 7 miles would be a robust choice for minimizing gasoline consumption, cost, and greenhouse gas emissions. For less frequent charging, every 20–100 miles, PHEVs release fewer GHGs, but HEVs are more cost effective. "
Retrofit electrification requires only one-fifth the energy required to build a new vehicle. This is called ACEV-to-PHEV conversion. There are several companies that are converting fossil fuel non-hybrid vehicles (also called all-combustion engine vehicles) to plug-in hybrids:
Colorado is going to offer $6,000 credit for PHEV conversions (in addition to a federal 10% credit up to $4,000 for qualifying vehicles).
|This section requires expansion. (February 2009)|
Aftermarket conversion of an existing production hybrid (a charge-maintaining hybrid) to a plug-in hybrid (called CHEV-to-PHEV conversion) typically involves increasing the capacity of the vehicle's battery pack and adding an on-board AC-to-DC charger. Ideally, the vehicle's powertrain software would be reprogrammed to make full use of the battery pack's additional energy storage capacity and power output.
Many early plug-in hybrid electric vehicle conversions have been based on the 2004 or later model Toyota Prius. Some of the systems have involved replacement of the vehicle's original NiMH battery pack and its electronic control unit. Others, such as A123 Hymotion, the CalCars Prius+, and the PiPrius, piggyback an additional battery back onto the original battery pack, this is also referred to as Battery Range Extender Modules (BREMs). Within the electric vehicle conversion community this has been referred to as a "hybrid battery pack configuration". Early lead–acid battery conversions by CalCars demonstrated 10 miles (15 km) of EV-only and 20 miles (30 km) of double mileage blended mode range.
EDrive Systems use Valence Technology Li-ion batteries and have a claimed 40 to 50 miles (64 to 80 km) of electric range. Other companies offering plug-in conversions or kits for the Toyota Prius (some of them also for Ford Escape Hybrid) include Hymotion, Hybrids Plus Manzanita Micro and OEMtek BREEZ (PHEV-30). AFS Trinity's XH-150 claims that it has created a functioning plug-in hybrid with a 40 miles (64 km) all-electric range and that it has solved the overheating problem that rapid acceleration can cause in PHEVs and extend battery life.
The EAA-PHEV project was conceived by CalCars and the Electric Auto Association in October 2005 to accelerate efforts to document existing HEVs and their potential for conversion into PHEVs. It includes a "conversion interest" page. The Electric Auto Association-PHEV "Do-It-Yourself" Open Source community's primary focus is to provide conversion instructions to help guide experienced converters through the process, and to provide a common design that could demonstrate multiple battery technologies. Many members of organizations such as CalCars and the EAA as well as companies like Hybrids Plus, Hybrid Interfaces of Canada, and Manzanita Micro participate in the development of the project.
Plug-In Supply, Inc. of Petaluma, California offers components and assemblies to build the Prius+, the plug-in conversion invented by CalCars. Their lead–acid battery box assembly forms a complete install package, providing access to the spare tire and containing twenty 12 volt lead–acid batteries and all high voltage components and control electronics. The "PbA Battery Box Assembly" is also available without batteries. It provides about 10 miles (16 km) of EV mode range. Conversion time was reduced by plug-in supply to one day.
Oemtek offers a Valence powered lithium iron phosphate conversion that should provide 50 miles (80 km) of all-electric range. The Motor Industry Research Association has announced a retrofit hybrid conversion kit that provides removable battery packs that plug into a wall outlet for charging. Poulsen Hybrid is developing a conversion kit that will add through-the-road plug-in hybrid capability to conventional vehicles by externally mounting electric motors onto two of the wheels.
MD-Tech offers a PHEV Kit for hybrid vehicles that acts as a hybrid battery re-charger. The kit supplies power to the hybrid battery without modifying the powertrain of the hybrid vehicle. It fits into the back of a hybrid vehicle, originally designed to fit under the rear floor of a Toyota Prius. The kit uses lithium iron phosphate cells in a battery supplying 4kWh of energy. This gives it a range of 30 km in charge-depleting, EV mode and provides a boost of power in blended mode. The battery charger uses mains electricity and takes 4–5 hours to charge. The battery supplies power to the DC to DC boost converter which regulates power to the hybrid battery. The converter output can be adjusted to set voltage and current output. A proprietary battery management system uses active battery balancing to monitor the battery state of health.
Enginer Inc. of Troy, Michigan offers universal plugin conversion kits with components and assemblies to build two stage hybrid battery system. Their lithium-ion battery box assembly forms a complete install package, providing access to the spare tire and containing 16/32 lithium phosphate battery cells, a DC/DC converter, a BMS and a charger. It provides about 10 miles (16 km) of EV mode range for under $2000 (2 kW·h model). Longer range 4 kW·h model is also available for $1000 more. Conversion time was reduced to two/three hours.
Each kilowatt hour of battery capacity in use will displace up to 50 U.S. gallons (190 l; 42 imp gal) of petroleum fuels per year (gasoline or diesel fuels). Also, electricity is multi-sourced and, as a result, it gives the greatest degree of energy resilience.
The actual fuel economy for PHEVs depends on their powertrain operating modes, their all-electric range, and the amount of driving between charges. If no gasoline is used the miles per gallon gasoline equivalent (MPG-e) depends only on the efficiency of the electric system. The first mass production PHEV available in the U.S. market, the 2011 Chevrolet Volt, with an EPA rated all-electric range of 35 miles (56 km), and an additional gasoline-only extended range of 344 miles (554 km) has an EPA combined city/highway fuel economy of 93 MPG-e in all-electric mode, and 37 mpg-US (6.4 L/100 km; 44 mpg-imp) in gasoline-only mode, for an overall combined gas-electric fuel economy rating of 60 mpg-US (3.9 L/100 km; 72 mpg-imp) equivalent (MPG-e). The EPA also included in the Volt's fuel economy label a table showing fuel economy and electricity consumed for five different scenarios: 30, 45, 60 and 75 miles (121 km) driven between a full charge, and a never charge scenario. According to this table the fuel economy goes up to 168 mpg-US (1.40 L/100 km; 202 mpg-imp) equivalent (MPG-e) with 45 miles (72 km) driven between full charges.
For the more comprehensive fuel economy and environment label that will be mandatory in the U.S. beginning in model year 2013, the National Highway Traffic Safety Administration (NHTSA) and Environmental Protection Agency (EPA) issued two separate fuel economy labels for plug-in hybrids because of their design complexity, as PHEVS can operate in two or three operating modes: all-electric, blended, and gasoline-only. One label is for series hybrid or extended range electric vehicle (like the Chevy Volt), with all-electric and gasoline-only modes; and a second label for blended mode or series-parallel hybrid, that includes a combination of both gasoline and plug-in electric operation; and gasoline only, like a conventional hybrid vehicle.
A further advantage of PHEVs is that they have potential to be even more efficient than conventional hybrids because a more limited use of the PHEV's internal combustion engine may allow the engine to be used at closer to its maximum efficiency. While a Prius is likely to convert fuel to motive energy on average at about 30% efficiency (well below the engine's 38% peak efficiency) the engine of a PHEV-70 would be likely to operate far more often near its peak efficiency because the batteries can serve the modest power needs at times when the combustion engine would be forced to run well below its peak efficiency. The actual efficiency achieved depends on losses from electricity generation, inversion, battery charging/discharging, the motor controller and motor itself, the way a vehicle is used (its duty cycle), and the opportunities to recharge by connecting to the electrical grid.
The Society of Automotive Engineers (SAE) developed their recommended practice in 1999 for testing and reporting the fuel economy of hybrid vehicles and included language to address PHEVs. An SAE committee is currently working to review procedures for testing and reporting the fuel economy of PHEVs. The Toronto Atmospheric Fund tested ten retrofitted plug-in hybrid vehicles that achieved an average of 5.8 litres per 100 kilometre or 40.6 miles per gallon over six months in 2008, which was considered below the technology's potential.
PHEV batteries also allow for an additional efficiency when converting solar power directly into a DC storage system, as opposed to converting the energy into AC home or building. DC to DC direct conversion is more efficient, therefore, potentially allowing the more efficient capture of solar energy.
In real world testing using normal drivers, some Prius PHEV conversions may not achieve much better fuel economy than HEVs. For example, a plug-in Prius fleet, each with a 30 miles (48 km) all-electric range, averaged only 51 mpg-US (4.6 L/100 km; 61 mpg-imp) in a 17,000-mile (27,000 km) test in Seattle, and similar results with the same kind of conversion battery models at Google's RechargeIT initiative. Moreover, the additional battery pack costs US$10,000–US$11,000.
The following table compares EPA's estimated out-of-pocket fuel costs and fuel economy ratings of all the plug-in hybrid electric vehicles rated by EPA in the U.S. by January 2013 versus the most fuel efficient gasoline-electric hybrid car, the Toyota Prius third generation, and EPA's average new 2013 vehicle, which has a fuel economy of 23 mpg-US (10 L/100 km; 28 mpg-imp). The table also shows the fuel efficiency for plug-in hybrids in all-electric mode expressed as KW-hrs/100 mile, the metric used by EPA to rate electric cars before November 2010.
|Comparison of out-of-pocket fuel costs and fuel economy for automobiles|
rated by EPA with MPGe and conventional MP(1)
(as displayed in the Monroney label and the US DoE fueleconomy.gov website)
|Ford Fusion Energi||2013||Electricity|
(34 kW-hrs/100 mi)
|108 mpg-e||92 mpg-e||$1.17||$950||The Energi did not use any gasoline|
for the first 21 miles in EPA tests,
but depending on the driving style,
the car may use both gasoline
and electricity during EV mode.
|Gasoline only||43 mpg||44 mpg||41 mpg||$2.03|
|Ford C-Max Energi||2013||Electricity|
(34 kW-hrs/100 mi)
|108 mpg-e||92 mpg-e||$1.17||$950||The Energi did not use any gasoline|
for the first 21 miles in EPA tests,
but depending on the driving style,
the car may use both gasoline
and electricity during EV mode.
|Gasoline only||43 mpg||44 mpg||41 mpg||$2.03|
|Chevrolet Volt||2013||Electricity only|
(35 kW-hrs/100 mi)
|-||-||$1.05||$900||The 2013 Volt is the most fuel efficient|
plug-in hybrid car with a combined
gasoline/electricity rating of 62 mpg-e
(City 63 mpg-e, Hwy 61 mpg-e).
|Gasoline only||37 mpg||35 mpg||40 mpg||$2.57|
|Toyota Prius PHV||2013||Electricity|
(29 kW-hrs/100 mi
plus 0.2 gallons/100 mi)
|-||-||$1.44||$950||After the first 11 miles the car|
functions like a regular Prius hybrid
|Gasoline only||50 mpg||51 mpg||49 mpg||$1.74|
|Chevrolet Volt||2012||Electricity only||94 mpg-e|
(36 kW-hrs/100 mi)
(36 kW-hrs/100 mi)
(37 kW-hrs/100 mi)
|Gasoline only||37 mpg||35 mpg||40 mpg||$2.57|
|Fisker Karma||2012||Electricity only|
(62 kW-hrs/100 mi)
|Gasoline only||20 mpg||20 mpg||21 mpg||$4.76|
|50 mpg||51 mpg||48 mpg||$1.74||$1,050||Most fuel efficient gasoline-electric|
hybrid car, together with the Prius c.
|Ford Taurus FWD|
(Average new car)
|2013||Gasoline only||23 mpg||19 mpg||29 mpg||$3.79||$2,300||Other 2013 models achieving 23 mpg|
include the Chrysler 200, Toyota Venza,
and Hyundai Santa Fe Sport 2WD.
|Notes: (1) Based on 45% highway and 55% city driving. Electricity cost of US$0.12/kw-hr, premium gasoline price of US$3.81 per gallon (used by the Volt and Karma), and regular gasoline price of US$3.49 per|
gallon (as of November 30, 2012). Conversion 1 gallon of gasoline=33.7 kW-hr. (Approx US$1.01 per litre premium and US$0.92 per litre regular)
One of the main barriers for the general adoption of all-electric cars is the range anxiety factor, the driver's fear of being stranded by a depleted battery before reaching the final destination. Plug-in hybrids, as opposed to pure electric cars, eliminate the range anxiety concerns because the gasoline engine serves as a back-up to recharge the battery to provide electric power to the electric motor, or to provide propulsion directly. Access to a regular fuel station guarantees that a PHEV has similar driving ranges as conventional gasoline-powered automobile.
As a response to range anxiety concerns, BMW is offering an optional limited capability gasoline range extender engine for its all-electric BMW i3. The range-extender option costs an additional US$3,850 in the United States, €4,710 (~ US$6,300) in France, and €4,490 (~ US$6,000) in the Netherlands. The range-extender option of the BMW i3 was designed to meet the California Air Resources Board (CARB) regulation for an auxiliary power unit (APU) called REx. According to rules adopted in March 2012 by CARB, the 2014 BMW i3 with a REx unit fitted will be the first car to qualify as a range-extended battery-electric vehicle or "BEVx." CARB describes this type of electric vehicle as "a relatively high-electric range battery-electric vehicle (BEV) to which an APU is added." The unit, which maintains battery charge at about 30% after the pack has been depleted in normal use, is strictly limited in the additional range it can provide.
One of the advantages of the plug-in hybrid design is that the generator can be completely decoupled from the traction. Unlike a conventional engine, which operates over a wide variety of power settings and operational conditions, the range extender can be operated under optimum conditions at all times. High-efficiency power sources that are not suitable for normal automotive use may be perfectly suitable for PEV use. These include advanced close-cycle steam engines, stirling engines, Wankel engines, and microturbines due primarily to their light weight and small size.
The Ontario Medical Association announced that smog is responsible for an estimated 9,500 premature deaths in its province every year. Plug-in hybrids in emission-free electric mode may contribute to the reduction of smog.
PHEVs and fully electric cars may allow for more efficient use of existing electric production capacity, much of which sits idle as operating reserve most of the time. This assumes that vehicles are charged primarily during off peak periods (i.e., at night), or equipped with technology to shut off charging during periods of peak demand. Another advantage of a plug-in vehicle is their potential ability to load balance or help the grid during peak loads. This is accomplished with vehicle-to-grid technology. By using excess battery capacity to send power back into the grid and then recharge during off peak times using cheaper power, such vehicles are actually advantageous to utilities as well as their owners. Even if such vehicles just led to an increase in the use of night time electricity they would even out electricity demand which is typically higher in the day time, and provide a greater return on capital for electricity infrastructure.
In the UK, VTG would need to comply with generation connection standard "G59/2", which means that it would need an earth rod at the premises, and would be unable to export more than 17 kW without the network firm's permission (which feeding onto one phase, i.e. for a normal house, would not be given - to maintain a balance of load across the three phases).
In October 2005, five Toyota engineers and one Asian AW engineer published an IEEE technical paper detailing a Toyota-approved project to add vehicle-to-grid capability to a Toyota Prius. Although the technical paper described "a method for generating voltage between respective lines of neutral points in the generator and motor of the THS-II (Toyota Hybrid System) to add a function for generating electricity", it did not state whether or not the experimental vehicle could be charged through the circuit, as well. However, the vehicle was featured in a Toyota Dream House, and a brochure for the exhibit stated that "the house can supply electricity to the battery packs of the vehicles via the stand in the middle of the garage", indicating that the vehicle may have been a plug-in hybrid.
In November 2005, more than 50 leaders from public power utility companies across the United States met at the Los Angeles Department of Water and Power headquarters to discuss plug-in hybrid and vehicle-to-grid technology. The event, which was sponsored by the American Public Power Association, also provided an opportunity for association members to plan strategies that public power utility companies could use to promote plug-in hybrid technology. Greg Hanssen and Peter Nortman of EnergyCS and EDrive attended the two-day session, and during a break in the proceedings, made an impromptu display in the LADWP parking lot of their converted Prius plug-in hybrid.
In September 2006, the California Air Resources Board held a Zero Emission Vehicle symposium that included several presentations on V2G technology. In April 2007, Pacific Gas and Electric Company showcased a PHEV at the Silicon Valley Leadership Alternative Energy Solutions Summit with vehicle-to-grid capability, and demonstrated that it could be used as a source of emergency home power in the event of an electrical power failure. Regulations intended to protect electricians against power other than from grid sources would need to be changed, or regulations requiring consumers to disconnect from the grid when connected to non-grid sources will be required before such backup power solutions would be feasible.
Jon Wellinghoff, from the US Federal Energy Regulatory Commission, coined the term "Cash-Back Hybrids" to describe payments to car owners for putting their batteries on the power grid. Batteries could also be offered in low-cost leasing or renting or by donation (including maintenance) to the car owners by the public utilities, in a vehicle-to-grid agreement.
Disadvantages of plug-in hybrids include the additional cost, weight, and size of a larger battery pack. According to a 2010 study by the National Research Council, the cost of a lithium-ion battery pack is about US$1,700/kW·h of usable energy, and considering that a PHEV-10 requires about 2.0 kW·h and a PHEV-40 about 8 kW·h, the manufacturer cost of the battery pack for a PHEV-10 is around US$3,000 and it goes up to US$14,000 for a PHEV-40. According to the same study, even though costs are expected to decline by 35% by 2020, market penetration is expected to be slow and therefore PHEVs are not expected to significantly impact oil consumption or carbon emissions before 2030, unless a fundamental breakthrough in battery technologies occurs.
|Cost comparison between a PHEV-10 and a PHEV-40|
(prices for 2010)
compared to conventional
upgrade at home
to a HEV
to a HEV(2)
|Notes: (1) Considers the HEV technology used in the Toyota Prius with a larger battery pack. The Prius Plug-in estimated all-electric range is 14.5 mi (23 km)|
(2) Assuming 15,000 miles per year.
According to the 2010 NRC study, although a mile driven on electricity is cheaper than one driven on gasoline, lifetime fuel savings are not enough to offset plug-ins high upfront costs, and it will take decades before the break even point is achieved. Furthermore, hundreds of billions of dollars in government subsidies and incentives are likely to be required to achieve a rapid plug-in market penetration in the U.S.
A 2013 study by the American Council for an Energy-Efficient Economy reported that battery costs came down from US$1,300 per kilowatt hour in 2007 to US$500 per kilowatt hour in 2012. The U.S. Department of Energy has set cost targets for its sponsored battery research of US$300 per kilowatt hour in 2015 and US$125 per kilowatt hour by 2022. Cost reductions through advances in battery technology and higher production volumes will allow plug-in electric vehicles to be more competitive with conventional internal combustion engine vehicles.
A study published in 2011 by the Belfer Center, Harvard University, found that the gasoline costs savings of plug-in electric cars over the vehicles’ lifetimes do not offset their higher purchase prices. This finding was estimated comparing their lifetime net present value at 2010 purchase and operating costs for the U.S. market, and assuming no government subidies. According to the study estimates, a PHEV-40 is US$5,377 more expensive than a conventional internal combustion engine, while a battery electric vehicle (BEV) is US$4,819 more expensive. The study also examined how this balance will change over the next 10 to 20 years, assuming that battery costs will decrease while gasoline prices increase. Under the future scenarios considered, the study found that BEVs will be significantly less expensive than conventional cars (US$1,155 to US$7,181 cheaper), while PHEVs, will be more expensive than BEVs in almost all comparison scenarios, and only less expensive than conventional cars in a scenario with very low battery costs and high gasoline prices. BEVs are simpler to build and do not use liquid fuel, while PHEVs have more complicated powertrains and still have gasoline-powered engines.
Lithium iron phosphate batteries from Valence Technologies were used in the first plug-in hybrids from CalCars. They are providing a conversion for the Toyota Prius priced at US$12,000. Hymotion also offers a conversion for US$10,000 but their conversion is only 5 kW where Oemtek's is 9 kW.
Many authors have assumed that plug-in recharging will take place overnight at home. However, residents of cities, apartments, dormitories, and townhouses might not have garages or driveways with available power outlets, and they might be less likely to buy plug-ins unless recharging infrastructure is developed. Electrical outlets or charging stations near their places of residence, or in commercial or public parking lots or streets or workplaces are required for these potential users to gain the full advantage of PHEVs. Even house dwellers might need to charge at the office or to take advantage of opportunity charging at shopping centers. However, this infrastructure is not in place today and it will require investments by both the private and public sectors.
Several cities in California and Oregon, and particularly San Francisco and other cities in the San Francisco Bay Area and Silicon Valley, as well as some local private firms such as Google and Adobe Systems, already have deployed charging stations and have expansion plans to attend both plug-ins and all-electric cars. In Google's case, its Mountain View campus has 100 available charging stations for its share-use fleet of converted plug-ins available to its employees. Solar panels are used to generate the electricity, and this pilot program is being monitored on a daily basis, with performance results published on the RechargeIT website.
Increased pollution is expected to occur in some areas with the adoption of PHEVs, but most areas will experience a decrease. A study by the ACEEE predicts that widespread PHEV use in heavily coal-dependent areas would result in an increase in local net sulfur dioxide and mercury emissions, given emissions levels from most coal plants currently supplying power to the grid. Although clean coal technologies could create power plants which supply grid power from coal without emitting significant amounts of such pollutants, the higher cost of the application of these technologies may increase the price of coal-generated electricity. The net effect on pollution is dependent on the fuel source of the electrical grid (fossil or renewable, for example) and the pollution profile of the power plants themselves. Identifying, regulating and upgrading single point pollution source such as a power plant—or replacing a plant altogether—may also be more practical. From a human health perspective, shifting pollution away from large urban areas may be considered a significant advantage.
According to a 2009 study by The National Academy of Science, "Electric vehicles and grid-dependent (plug-in) hybrid vehicles showed somewhat higher nonclimate damages than many other technologies." Efficiency of plug-in hybrids is also impacted by the overall efficiency of electric power transmission. Transmission and distribution losses in the USA were estimated at 7.2% in 1995 and 6.5% in 2007. By life cycle analysis of air pollution emissions, natural gas vehicles are currently the lowest emitter.
Electric utility companies generally do not utilize flat rate pricing. For example, Pacific Gas and Electric (PG&E) normally charges $0.10 per kilowatt hour (kW·h) for the base tier, but additional tiers are priced as high as $0.30 per kW·h to customers without electric vehicles. Some utilities offer electric vehicle users a rate tariff that provides discounts for off-peak usage, such as overnight recharging. PG&E offers a special, discounted rate for plug-in and other electric vehicle customers, the "Experimental Time-of-Use Low Emission Vehicle rate." That tariff gives people much cheaper rates if they charge at night, especially during the summer months.
The additional electrical utilization required to recharge the plug-in vehicles could push many households in areas that do not have off-peak tariffs into the higher priced tier and negate financial benefits. Without an off-peak charging tariff, one study of a certain PHEV-20 model having an all-electric range of 20 miles, gasoline-fueled efficiency of 52.7 mi/gal U.S., and all-electric efficiency of 4 mi/kW·h, found that household electricity customers who consumed 131%–200% of baseline electricity at $0.220/(kW·h) would see benefits if gasoline was priced above US$2.89/US gal; those that consumed 201%–300% of baseline electricity at $0.303/(kW·h) would only see benefits if gas was priced above $3.98; and households consuming over 300% of baseline electricity at $0.346/(kW·h) would only see benefits if gasoline was priced above $4.55 (USD/gal). Off-peak tariff rates can lower the break-even point. The PG&E tariff would change those break-even gasoline prices to USD $1.96, $3.17 and $3.80 per gallon, respectively, for the given PHEV and usage pattern in question.
Customers under such tariffs could see significant savings by being careful about when the vehicle was charged, for example, by using a timer to restrict charging to off-peak hours. Thus, an accurate comparison of the benefit requires each household to evaluate its current electrical usage tier and tariffs weighed against the cost of gasoline and the actual observed operational cost of electric mode vehicle operation.
Current technology for plug-ins is based on the lithium-ion battery and an electric motor, and the demand for lithium, heavy metals and other rare elements (such as neodymium, boron and cobalt) required for the batteries and powertrain is expected to grow significantly due to the incoming market entrance of plug-ins and electric vehicles in the mid and long term. Some of the largest world reserves of lithium and other rare metals are located in countries with strong resource nationalism, unstable governments or hostile to U.S. interests, raising concerns about the risk of replacing dependence on foreign oil with a new dependence on hostile countries to supply strategic materials.
Currently, the main deposits of lithium are found in China and South America throughout the Andes mountain chain. In 2008 Chile was the leading lithium metal producer, followed by Australia, China, and Argentina. In the United States lithium is recovered from brine pools in Nevada. Nearly half the world's known reserves are located in Bolivia, and according to the US Geological Survey, Bolivia's Salar de Uyuni desert has 5.4 million tons of lithium, which can be used to make lithium batteries for hybrid and electric vehicles. Other important reserves are located in Chile, China, and Brazil. Regarding rare earth elements, most reserves are located in China, which controls the world market for these elements.
At low speeds, electric-drive cars produced less roadway noise as compared to vehicles propelled by internal combustion engines. Blind people or the visually impaired consider the noise of combustion engines a helpful aid while crossing streets, hence plug-in electric cars and hybrids could pose an unexpected hazard. Tests have shown that this is a valid concern, as vehicles operating in electric mode can be particularly hard to hear below 20 mph (30 km/h) for all types of road users and not only the visually impaired. At higher speeds, the sound created by tire friction and the air displaced by the vehicle start to make sufficient audible noise.
The Government of Japan, the U.S. Congress, and the European Parliament passed legislation to regulate the minimum level of sound for hybrids and plug-in electric vehicles when operating in electric mode, so that blind people and other pedestrians and cyclists can hear them coming and detect from which direction they are approaching. As of March 2013[update], most of the hybrids and plug-in electric cars available in the United States make warning noises using a speaker system.
The effect of PHEVs on greenhouse emissions is complex. Plug-in hybrid vehicles operating on all-electric mode do not emit harmful tailpipe pollutants from the onboard source of power. The clean air benefit is usually local because depending on the source of the electricity used to recharge the batteries, air pollutant emissions are shifted to the location of the generation plants. In the same way, PHEVs do not emit greenhouse gases from the onboard source of power, but from the point of view of a well-to-wheel assessment, the extent of the benefit also depends on the fuel and technology used for electricity generation. From the perspective of a full life cycle analysis, the electricity used to recharge the batteries must be generated from renewable or clean sources such as wind, solar, hydroelectric, or nuclear power for PEVs to have almost none or zero well-to-wheel emissions. On the other hand, when PEVs are recharged from coal-fired plants, they usually produce slightly more greenhouse gas emissions than internal combustion engine vehicles. In the case of plug-in hybrid electric vehicle when operating in hybrid mode with assistance of the internal combustion engine, tailpipe and greenhouse emissions are lower in comparison to conventional cars because of their higher fuel economy.
There has been much debate over the potential GHG emissions reductions that can be achieved with PHEV. A study by the Electric Power Research Institute reports that a 338 TW·h or 5.8% increase in power generation needed as a result of PHEV. In the same report the EPRI also states that CO2 emissions could increase by 430 million metric tons. The article concludes:
A study by the American Council for an Energy Efficient Economy (ACEEE) predicts that, on average, a typical American driver is expected to achieve about a 15% reduction in net CO
2 emissions compared to the driver of a regular hybrid, based on the 2005 distribution of power sources feeding the US electrical grid. The ACEEE study also predicts that in areas where more than 80% of grid-power comes from coal-burning power plants, local net CO
2 emissions will increase, while for PHEVs recharged in areas where the grid is fed by power sources with lower CO
2 emissions than the current average, net CO
2 emissions associated with PHEVs will decrease correspondingly.
A 2007 joint study by the Electric Power Research Institute (EPRI) and the Natural Resources Defense Council (NRDC) similarly found that the introduction of PHEVs into America’s consumer vehicle fleet could achieve significant greenhouse gas emission reductions. The EPRI-NRDC report estimates that, between 2010 and 2050, a shift toward PHEV use could reduce GHG emissions by 3.4 to 10.4 billion metric tons. The magnitude of these reductions would ultimately depend on the level of PHEV market penetration and the carbon intensity of the US electricity sector. In general, PHEVs can be viewed as an element in the "Pacala and Socolow wedges" approach which shows a way to stabilize CO
2 emissions using a portfolio of existing techniques, including efficient vehicles.
A 2008 study at Duke University suggests that for PHEV's to reduce greenhouse gas emissions more than hybrids a carbon pricing signal that encourages the development of low carbon power is needed. RAND also in 2008 studied the questions of a carbon tax, carbon cap and trade systems, increasing gasoline tax, and providing renewable energy subsidies under various economic conditions and vehicle type availabilities. RAND found that subsidies were able to provide a smoother transition to new energy sources, especially in the face of energy source price volatility, because subsidies can be structured according to relative costs between renewables and fossil fuel, while taxes and carbon trading schemes alone do not take relative prices of energy into account.
The Minnesota Pollution Control Agency found that if Minnesota's fleet of vehicles making lengthy trips were replaced by plug-in hybrids, CO
2 emissions per vehicle would likely decrease. However, unless more than 40% of the electricity used to charge the vehicles were to come from non-polluting sources, replacing the vehicles with non-plug-in hybrids would engender a larger decrease in CO
2 emissions. Plug-in hybrids use less fuel in all cases, and produce much less carbon dioxide in short commuter trips, which is how most vehicles are used. The difference is such that overall carbon emissions would decrease if all internal combustion vehicles were converted to plug-ins.
In 2009 researchers at Argonne National Laboratory adapted their GREET model to conduct a full well-to-wheels (WTW) analysis of energy use and greenhouse gas (GHG) emissions of plug-in hybrid electric vehicles for several scenarios, considering different on-board fuels and different sources of electricity generation for recharging the vehicle batteries. Three US regions were selected for the analysis, California, New York, and Illinois, as these regions include major metropolitan areas with significant variations in their energy generation mixes. The full cycle analysis results were also reported for the US generation mix and renewable electricity to examine cases of average and clean mixes, respectively This 2009 study showed a wide spread of petroleum use and GHG emissions among the different fuel production technologies and grid generation mixes. The following table summarizes the main results:
|PHEV well-to-wheels Petroleum energy use and greenhouse gas emissions|
for an all-electric range between 10 and 40 miles (16 and 64 km) with different on-board fuels.(1)
(as a % relative to an internal combustion engine vehicle that uses fossil fuel gasoline)
and Ultra-low sulfur diesel
|E85 fuel from|
corn and switchgrass
|Petroleum energy use reduction|
|GHG emissions reduction(2)|
|Source: Center for Transportation Research, Argonne National Laboratory (2009). See Table 1. Notes: (1) Simulations for year 2020|
with PHEV model year 2015. (2) No direct or indirect land use changes included in the WTW analysis for bio-mass fuel feedstocks.
The Argonne study found that PHEVs offered reductions in petroleum energy use as compared with regular hybrid electric vehicles. More petroleum energy savings and also more GHG emissions reductions were realized as the all-electric range increased, except when electricity used to recharged was dominated by coal or oil-fired power generation. As expected, electricity from renewable sources realized the largest reductions in petroleum energy use and GHG emissions for all PHEVs as the all-electric range increased. The study also concluded that plug-in vehicles that employ biomass-based fuels (biomass-E85 and -hydrogen) may not realize GHG emissions benefits over regular hybrids if power generation is dominated by fossil sources.
A 2008 study by researchers at Oak Ridge National Laboratory analyzed oil use and greenhouse gas (GHG) emissions of plug-in hybrids relative to hybrid electric vehicles under several scenarios for years 2020 and 2030. Each type of vehicle was assumed to run 20 miles (32 km) per day and the HEV was assumed to have a fuel economy of 40 miles per US gallon (5.9 L/100 km; 48 mpg-imp). The study considered the mix of power sources for 13 U.S. regions, generally a combination of coal, natural gas and nuclear energy, and to a lesser extend renewable energy. A 2010 study conducted at Argonne National Laboratory reached similar findings, concluding that PHEVs will reduce oil consumption but could produce very different greenhouse gas emissions for each region depending on the energy mix used to generate the electricity to recharge the plug-in hybrids. The following table summarizes the main results of the Oak Ridge National Laboratory study for the 2020 scenario:
|Comparison of carbon emissions and oil consumption by plug-in hybrids relative to hybrid electric vehicles (HEVs)|
by U.S. regional power generation sources on 2020
relative to HEVs
relative to HEVs
|States included in the region(2)|
|Plug-in hybrid||All-electric mode||Plug-in hybrid||All-electric mode|
|-20.0%||-37.2%||-47.0%||-99.6%||Includes ID, MT, NV, OR, UT, SD, WA, and WY.|
|New England||Natural gas|
|-11.4%||-17.4%||-44.3%||-93.5%||Includes CT, MA, ME, NH, RI, and VT.|
|Lower Midwest||Natural gas|
|-11.0%||-16.4%||-46.9%||-99.4%||Includes AR, KS, LA, NM, OK, and TX.|
|-9.40%||-12.8%||-46.9%||-99.4%||Includes AZ, CO, NM, NV, and TX.|
|-1.2%||+6.1||-45.4%||-95.9%||Includes DC, DE, MD, ME, NJ, and PA.|
|Upper Midwest||Natural gas|
|-0.8%||+7.2%||-46.7%||-99.0%||Includes IA, MN, MT, ND, NE, SD, and WI.|
|+2.4%||+14.4%||-46.7%||-98.9%||Includes AL, GA, LA, MS, NC, SC, and TN.|
|+7.8%||+27.0%||-46.6%||-98.7%||Includes IN, KY, MI, OH, VA, and WV.|
|+11.7%||+36.0%||-46.5%||-98.6%||Includes IA, IL, MI, MO, and WI.|
|Notes: (1) Regions as defined by the North American Electric Reliability Corporation. (2) Some states appear in more than one region because parts of them belong to different regions.|
The BYD F3DM became the world's first mass-produced plug-in hybrid compact sedan as it went on sale in China to government agencies and corporations on December 15, 2008. The F3DM had an all-electric range of 100 kilometers (60 mi). Sales to the general public began in Shenzhen in March 2010 but because the F3DM nearly doubled the price of cars that run on conventional fuel, BYD Auto was counting on subsidies from the local government to make the plug-in attractive to personal buyers. The F3DM was sold for 149,800 yuan (about US$21,900), and during its first year in the market the F3DM only sold 48 vehicles. During 2010, 417 units were sold, and cumulative sales in China reached 3,284 units through October 2013. Production of the BYD F3DM was ended due to low sales, and it was replaced by the BYD Qin.
Deliveries of the Chevrolet Volt began in December 2010, initially only in selected U.S. markets, and became available nationwide in November 2011. The Volt has a United States Environmental Protection Agency rated all electric range of 35 mi (56 km). Deliveries of the 2012 Volt began in Canada in September 2011. The first deliveries of the Chevrolet Volt in Europe took place on November 30, 2011. The European version of the Volt, the Opel Ampera, was released to customers in Europe in February 2012. Deliveries of the right-hand drive Vauxhall Ampera in the UK began in May 2012. The Holden Volt was released in Australia in December 2012.
The Volt/Ampera family of vehicles was the world's best selling plug-in electric car in 2012 with 31,400 units sold, and ranked in the 432nd place among all models sold worldwide in 2012. The Opel/Vauxhall Ampera was Europe's top selling plug-in electric car in 2012 with 5,268 units representing a market share of 21.5% of the region's plug-in electric passenger car segment.
As of January 2014[update], with global sales of about 70,000 units, the Volt/Ampera family of vehicles is the world's second best selling plug-in electric car ever, after the Nissan Leaf, which has sold over 100,000 units worldwide. Volt sales are led by the United States with 54,552 units sold through December 2013. Over 8,500 Opel/Vauxhall Amperas have been sold in Europe through December 2013, with the Netherlands as the leading market with 4,922 Amperas delivered through December 2013. As of December 2013[update], the Volt is the top selling plug-in electric car in the United States, and the Volt/Ampera family is the world's best selling plug-in hybrid.
Retail deliveries of the Fisker Karma began in November 2011. The Karma had an EPA rated all-electric range of 32 mi (51 km). Production was suspended in November 2012 due to financial difficulties, with about 2,450 Karmas built since 2011. As a result of flash floods caused by Hurricane Sandy in October 2012, 16 Karmas caught fire and another 330 units were lost when an entire shipment from Europe was flooded while being parked at Port Newark-Elizabeth Marine Terminal. Fisker Automotive filed for bankruptcy in November 2013, after the U.S. Department of Energy auctioned its debt and sold it to Hybrid Technology LLC. Around 2,100 units were sold in North America and Europe through December 2013, led by the United States with over 1,600 units sold. The Netherlands was the top selling European market for the Karma, with 188 units sold through December 2013.
The Toyota Prius Plug-in Hybrid was released in Japan in January 2012, and deliveries in the United States began in late February 2012. The Prius PHV total all-electric range in blended mode is 11 mi (18 km) as rated by EPA. During 2012, its first year in the market, global sales reached 27,181 units. As of December 2013[update], the Prius Plug-in Hybrid has sold over 45,000 units worldwide, led by the U.S. with 24,838 units sold, followed by Japan with 12,600 units through March 2013, and Europe with over 7,600 units through December 2013, led by the Netherlands with 3,891 units through December 2013.
The Ford C-Max Energi has an all-electric range of 21 mi (34 km) and was released in the U.S. by mid October 2012. The EPA rated the Energi combined city/highway fuel economy in all-electric mode at 100 MPG-e (2.4 L/100 km), and 108 MPG-e (2.2 L/100 km) for city driving and 92 MPG-e (2.6 L/100 km) in highway. A total of 9,528 units have been sold in the U.S. through December 2013.
The Volvo V60 Plug-in Hybrid, the world's first diesel plug-in hybrid, has an all-electric range of up to 50 km (31 mi), and a fuel economy of 124 miles per gallon of gasoline equivalent (1.8 l/100 km), with carbon dioxide emissions averaging 49 g/km. Retail deliveries began in Sweden in late 2012 and the rest of Europe in early 2013. The diesel PHV is not expected to be available in the U.S. In September 2012, Volvo announced that the first 1,000 units were sold out before the model year 2013 vehicles were delivered to the dealerships. The carmaker ramped up production of the 2014 model year to 5,000 units for 2013. Over 7,700 units have been delivered as of December 2013[update], with sales led by the Netherlands with 6,283 units, Sweden with 643 units, and France with 241 units. The V60 PHEV is the top selling plug-in hybrid in Europe accounting for the segment sales during the first eleven months of 2013.
The Honda Accord Plug-in Hybrid, with an all-electric range of 13 mi (21 km), was released in the U.S. in January 2013 and is available only in California and New York. A total of 526 units have been sold in the U.S. through December 2013. The Mitsubishi Outlander P-HEV was released in the Japanese market also in January 2013, becoming the first SUV plug-in hybrid in the market. The European version was released in Europe in October 2013. The introduction in the United States was delayed until 2015 due to problems in the initial production batch. The SUV has an all-electric range of 60 km (37 mi), and a fuel economy of 157 miles per gallon of gasoline equivalent (MPG-e). Over 17,800 units have been sold through December 2013, with 9,608 units sold in Japan and 8,197 in Europe. European sales are led by the Netherlands with 8,038 units delivered through December 2013, where the Outlander P-HEV ranked for two months in-a-row, November and December 2013, as the top selling new car in the country. The Outlander P-HEV also became the top selling plug-in electric car in the Netherlands as of December 2013[update].
Deliveries of the Ford Fusion Energi began in the United States in February 2013. The Fusion Energi has an all-electric range of 21 mi (34 km) and an equivalent fuel economy EPA rating of 100 MPG-e (2.4 L gasoline equivalent/100 km). A total of 6,089 units have been sold in the U.S. through December 2013.
The limited edition McLaren P1 supercar was released in the UK in October 2013. The P1 has an all-electric range of 6.2 mi (10.0 km) on the combined New European Driving Cycle. Production is limited to 375 units to maintain exclusivity. Pricing starts at GB£866,000 (€1,030,000 or US$1,350,000). With only 12 units manufactured by mid November 2013, the entire P1 production was sold out, with about 75% of the customers opting for some level of customization, raising the average sales price to GB£1 million (€1,2 million or US$1,6 million).
The Porsche Panamera S E-Hybrid was released in the U.S. in November 2013. The Panamera S E-Hybrid has an all-electric range of 32 km (20 mi) under the New European Driving Cycle (NEDC) test.
Retail sales of the BYD Qin began in Costa Rica in November 2013, and sales in other Latin American countries are scheduled to begin in 2014. The start of retail sales in the Chinese market was rescheduled several times, and deliveries began in mid December 2013. The Cadillac ELR was released to retail customers in the U.S. in December 2013. The ELR is a limited production luxury coupé that shares the powertrain of the Chevrolet Volt and has an all-electric range of about 37 miles (60 km).
Before the launch of mass production plug-in hybrids, conversion kits and services were available in the United States to convert production model hybrid electric vehicles to plug-ins. The regular Toyota Prius has been commercially converted, using these aftermarket kits and tax incentives, to a plug-in hybrid by CalCars and a number of third-party companies. On a smaller scale, PHEVs have been sold as commercial passenger vans, utility trucks, general and school buses, motorcycles, scooters, and military vehicles. Hybrid Electric Vehicle Technologies, Inc converts diesel buses to plug-in hybrids, under contract for the Chicago Transit Authority. Fisher Coachworks is developing a plug-in hybrid, the Fisher GTB-40, which is expected to get about twice the mileage of a regular hybrid electric bus.
Plug-in hybrid sales in 2012 were led by the United States with a 70% market share of global sales, followed by Japan with a 12%, the Netherlands with 8%, and Canada and China with 2% each. As of December 2013[update], the United States is the world's largest plug-in hybrid car market with 95,589 units sold, followed by the Netherlands with 24,512 plug-in hybrids registered through December 2013, and Japan with over 22,200 units sold through December 2013. The Netherlands is the country with highest plug-in hybrid market penetration, with 1.45 vehicles registered per 1,000 people. Most of the growth of the Dutch plug-in hybrid stock took place in 2013, with 20,164 units sold that year representing a rate of growth of 365% from 2012.
As of December 2013[update], the Netherlands, Sweden and the United States have the largest shares of plug-in hybrid sales as percentage of total plug-in electric passenger vehicle sales. Accounting for cumulative registrations between 2009 and 2013, plug-in hybrids represent 83.5% of the Dutch plug-in car market (28,673 units). Out of 2,651 plug-in electric cars sold in Sweden between 2011 and December 2013, plug-in hybrids have a 66.6% share. In the United States, out of over 167,600 plug-in electric cars sold through December 2013, plug-in hybrids represent 57.0% of total plug-in car sales since December 2010. In Japan, plug-in hybrids represent 31.1% of the 71,324 plug-in electric vehicles sold in the country since 2009 through December 2013.
In November 2013 the Netherlands became the first country where a plug-in hybrid topped the monthly ranking of new car sales. During November sales were led by the Mitsubishi Outlander P-HEV with 2,736 units, capturing a market share of 6.8% of new passenger cars sold that month. Again in December 2013 the Outlander P-HEV ranked as the top selling new car in the country with 4,976 units, representing a 12.6% market share of new car sales. These record sales allowed the Netherlands to become the second country, after Norway, where plug-in electric cars have topped the monthly ranking of new car sales. The dominance of plug-in hybrids in the Netherlands is reflected by the fact that, since their inception up to December 2013, four out of the top five selling plug-in electric models are plug-in hybrids. Dutch PEV sales through December 2013 are led by the Mitsubishi Outlander P-HEV (8,038), followed by the Volvo V60 Plug-in Hybrid (6,283), Opel Ampera (4,922 units), and Prius PHV (3,891). Ranking fifth is the Tesla Model S with 1,192 units, which passed the Chevrolet Volt (1,062 units) in December 2013.
The following table presents sales of plug-in hybrid models since the introduction of the first modern production plug-in hybrid vehicle in December 2008, and summarizes sales in the top selling countries for each model through December 2013:
|Plug-in hybrid global sales and top markets by country or region|
between December 2008 and December 2013
|Global sales||Top selling markets|
35 mi (56 km)
|Global sales through December 2013.|
|US||54,552||Chevrolet Volts through December 2013.|
|Netherlands||5,984||4,922 Amperas and 1,062 Volts through December 2013.|
|Canada||2,431||Chevrolet Volts through December 2013.|
|Germany||1,477||1,404 Amperas and 73 Volts through December 2013.|
|UK||699||609 Amperas and 90 Volts through June 2013.|
|Switzerland||535||346 Amperas and 189 Volts through December 2013.|
|France||304||247 Amperas and 57 Volts through December 2013.|
|Belgium||241||201 Amperas and 40 Volts through December 2013.|
|Norway||230||229 Amperas and 1 Volt through December 2013.|
|Austria||226||207 Amperas and 19 Volts through December 2013.|
|Australia||181||Holden Volts through December 2013.|
|Sweden||149||109 Amperas and 40 Volts through December 2013.|
|Toyota Prius PHV|
11 mi (18 km)
|Global sales through December 2013.|
|US||24,838||Sales through December 2013.|
|Japan||12,600||Sales through March 2013.|
|Netherlands||3,891||Sales through December 2013.|
|UK||979||Sales through December 2013.|
|Sweden||875||Sales through December 2013.|
|France||806||Sales through December 2013.|
|Norway||327||Sales through December 2013.|
|Canada||275||Sales through December 2013.|
|Finland||118||Sales through December 2013.|
|Spain||109||Sales through December 2013.|
|Mitsubishi Outlander P-HEV|
60 km (37 mi)
|Sales through December 2013, of which, 8,197 were sold in Europe.|
|Japan||9,608||Sales through December 2013.|
|Netherlands||8,038||Sales through December 2013.|
|Sweden||96||Sales through December 2013.|
|Ford C-Max Energi|
21 mi (34 km)
|9,727||Sales through December 2013.|
|US||9,528||Sales through December 2013.|
|Canada||199||Sales through December 2013.|
|Volvo V60 Plug-in Hybrid|
50 km (31 mi)
|Sales through December 2013.|
|Netherlands||6,283||Sales through December 2013.|
|Sweden||643||Sales through December 2013.|
|France||241||Sales through December 2013.|
|Belgium||153||Sales through December 2013.|
|Italy||135||Sales through December 2013.|
|Norway||89||Sales through December 2013.|
|Germany||73||Sales through December 2013.|
|Finland||66||Sales through December 2013.|
|Austria||31||Sales through December 2013.|
|Ford Fusion Energi|
21 mi (34 km)
|6,205||Sales through December 2013.|
|US||6,089||Sales through December 2013.|
|Canada||116||Sales through December 2013.|
60 mi (97 km)
|3,295||Sales through December 2013.|
Production ended in 2013. The F3DM was substituted by the BYD Qin.
|China||3,284||Sales through December 2013.|
|Europe||11||Sales through October 2012.|
32 mi (51 km)
|North America and Europe through December 2013.|
Production was suspended in November 2012 due to financial difficulties.
|US||1,635||Sales through December 2013.|
|Netherlands||188||Sales through December 2013.|
|Canada||90||Sales through December 2013.|
|Switzerland||69||Sales through December 2013.|
|Belgium||65||Sales through December 2013.|
|Germany||50||Sales through December 2013.|
|France||33||Sales through December 2013.|
|Sweden||21||Sales through December 2013.|
|Austria||13||Sales through December 2013.|
|Honda Accord Plug-in Hybrid|
13 mi (21 km)
|526||US||526||Sales through December 2013.|
|Porsche Panamera S E-Hybrid|
32 km (20 mi)
|190||Global sales through December 2013.|
|US||86||Sales through December 2013.|
|France||90||Sales through December 2013.|
|Germany||12||Sales through December 2012.|
70 km (43 mi)
|142||CHN||142||Sales through December 2013.|
35 mi (56 km)
|6||US||6||Sales through December 2013.|
|Total global plug-in hybrid sales|
(Sales from December 2008 through December 2013)
|US||95,589||Sales between December 2010 and December 2013.|
|Netherlands||24,512||Registrations through December 2013.|
|Japan||Over 22,200||Sales through December 2013.|
|China||Over 3,400||Sales through December 2013.|
|Canada||About 3,100||Sales through December 2013.|
|UK||2,064||Registration since January 2012 through December 2013.|
|Sweden||1,765||Sales through December 2013.|
|Germany||About 1,600||Sales through December 2013.|
|France||1,474||Sales through December 2013.|
|Norway||About 650||Registrations through December 2013.|
|Switzerland||Over 600||Sales through December 2013.|
Plug-in vehicles ongoing demonstration trials include the Ford Escape Plug-in Hybrid, Volvo V70 Plug-in Hybrid, Suzuki Swift Plug-in, Audi A1 e-tron, Dodge Ram 1500 Plug-in Hybrid, and Volkswagen Golf Variant Twin Drive. PHEVs scheduled for market launch between in 2014 and 2015 include the Porsche 918 Spyder, Volkswagen XL1 (limited edition), Audi A3 Sportback e-tron, BMW i8, and Mercedes-Benz S 500 Plug-in Hybrid.
Several countries have established grants and tax credits for the purchase of new plug-in electric vehicles (PEVs) including plug-in hybrid electric vehicles, and usually the economic incentive depends on battery size. The U.S. offers a federal income tax credit up to US$7,500, and several states have additional incentives. The U.K. offers a Plug-in Car Grant up to a maximum of GB£5,000 (US$7,600). As of April 2011, 15 of the 27 European Union member states provide tax incentives for electrically chargeable vehicles, which includes all Western European countries plus the Czech Republic and Romania. Also 17 countries levy carbon dioxide related taxes on passenger cars as a disincentive. The incentives consist of tax reductions and exemptions, as well as of bonus payments for buyers of all-electric and plug-in hybrid vehicles, hybrid vehicles, and some alternative fuel vehicles.
Incentives for the development of PHEVs are included in the Energy Independence and Security Act of 2007. The Energy Improvement and Extension Act of 2008, signed into law on October 3, 2008, grants a tax credits for the purchase of PHEVs. President Barack Obama's New Energy for America calls for deployment of 1 million plug-in hybrid vehicles by 2015, and on March 19, 2009, he announced programs directing $2.4 billion to electric vehicle development.
The American Recovery and Reinvestment Act of 2009 modifies the tax credits, including a new one for plug-in electric drive conversion kits and for 2 or 3 wheel vehicles. The ultimate total included in the Act that is going to PHEVs is over $6 billion.
In March 2009, as part of the American Recovery and Reinvestment Act, the US Department of Energy announced the release of two competitive solicitations for up to $2 billion in federal funding for competitively awarded cost-shared agreements for manufacturing of advanced batteries and related drive components as well as up to $400 million for transportation electrification demonstration and deployment projects. This announcement will also help meet the President Barack Obama's goal of putting one million plug-in hybrid vehicles on the road by 2015.
Public deployments also include:
GM's roadmap for plug-in ready communities includes: consumer incentives to make this early technology more affordable; public and workplace charging infrastructure; consumer-friendly electricity rates and renewable electricity options; government and corporate vehicle purchases; supportive permitting and codes for vehicle charging; and other incentives such as high-occupancy-vehicle (HOV) lanes access
Electrification of transport (electromobility) is a priority in the European Union Research Programme. It also figures prominently in the European Economic Recovery Plan presented November 2008, in the frame of the Green Car Initiative. DG TREN will support a large European "electromobility" project on electric vehicles and related infrastructure with a total budget of around € 50 million as part of the Green Car Initiative.
Organizations that support plug-in hybrids include the World Wide Fund for Nature, its International Director General James Leape remarked, "the cars of the future ... should, increasingly, be powered by electricity."
CalCars (with their PHEV news service and "What car makers are saying about PHEVs") is dedicated only to the PHEV and has proposed a Prepayment Plan, where buyers would pay $1,000 to reserve a plug-in car and the federal government would match each payment with $9,000, all of which would go to carmakers. CalCars is also promoting public funds for conversion of internal combustion engines to plug-in vehicles.
Other supportive organizations are Plug In America, the Alliance for Climate Protection, Friends of the Earth, the Rainforest Action Network, Rocky Mountain Institute (Project Get Ready), the San Francisco Bay Area Council, the Apollo Alliance, the Set America Free Coalition, the Silicon Valley Leadership Group, and the Plug-in Hybrid Electric School Bus Project,
FPL and Duke Energy has said that by 2020 all new purchases of fleet vehicles will be plug-in hybrid or all-electric.
Some battery formats and chemistries (nickel–metal hydride batteries) suitable for use in PHEVs are tightly patented and were not licensed for use by PHEV manufacturers, thereby slowed the development of electric cars and PHEVs before the 2008 Oil Crisis.
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