The history of plug-in hybrid electric vehicles (PHEVs) spans a little more than a century, but most of the significant commercial developments have taken place after 2002. The revival of interest in this automotive technology together with all-electric cars is due to advances in battery and power management technologies, and concerns about increasingly volatile oil prices and supply disruption, and also the need to reduce greenhouse gas emissions.See Introduction Between 2003 and 2010, most PHEVs were conversions of production hybrid electric vehicles, and the most prominent PHEVs were aftermarket conversions of 2004 or later Toyota Prius, which have had plug-in charging and more lead–acid batteries added and their electric-only range extended.
Global sales of plug-in hybrids grew from over 300 units in 2010 to 222,000 in 2015 and 7.2 million in 2025. , China is the world's largest plug-in hybrid car market with a stock of 15 million units, followed by the United States with 1.9 million vehicles, Germany with 1.1 million, the UK with 860,000 and France with 810,000. , there are about 25 million plug-in hybrid electric cars in the world, about one third of the total stock of 75 million plug-in electric cars. In the half year to , the BYD Song Plus was the world's top selling plug-in hybrid car, with 188,500 units sold (5.4% of all PHEV sales) over the period. BYD models accounted for seven of the top ten best-selling PHEVs over this period, with the Li Auto L6 (96,400), Galaxy Starship 7 (70,900) and Aito M9 (58,700) also among the top ten.
1899–1999
Hybrid vehicles were produced beginning as early as 1899 by Lohner–Porsche. 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 July 1969 issue of Popular Science magazine 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 trans-axle. The gasoline-powered engine was connected to the trans-axle via a worm gear. The car could be plugged into a standard 110 Volt AC outlet for recharging.
In 1971, Dr. Andy Frank, the inventor of the modern PHEV, begins working on hybrids and PHEVs. He is professor of Mechanical and Aeronautical Engineering at the University of California at Davis.
The September 1975 issue of Popular Mechanics magazine featured a cover story on an experimental "turbo-electric" hybrid that "plugs in overnight for thrifty driving around town." Built by electronics engineer Harry Grepke, the vehicle used eight 12-volt truck batteries and a turbine genset. Grepke claimed an all-electric range of .
In 1989, Audi produced its first iteration of the Audi Duo, a plug-in parallel hybrid based on the Audi 100 Avant Quattro. This car had a Siemens electric motor which drove the rear wheels. A trunk-mounted nickel-cadmium battery supplied energy to the motor that drove the rear wheels. The vehicle's front wheels were powered by a 2.3-litre five-cylinder engine with an output of . The intent was to produce a vehicle which could operate on the engine in the country and electric mode in the city. Mode of operation could be selected by the driver. Just ten vehicles are believed to have been made; one drawback was that due to the extra weight of the electric drive, the vehicles were less efficient when running on their engines alone than standard Audi 100s with the same engine.
Beginning around 1990, Professor Andy Frank of the University of California, Davis began using student teams to build operational prototype Plug-in hybrid electric vehicles. His work attracted industry support and funding from Nissan, Koyo Seiko, General Motors, Saturn, Ford, Visteon, JATCO, Ovonics, the Defense Advanced Research Project Agency (DARPA), Sacramento Municipal Utility District, Southern California Edison, the United States Department of Energy, and others. The UC Davis PHEVs won several DOE/USCAR "Future Car" and "Future Truck" national competitions.
Inspired by his work as an EV1 propulsion system engineer, Jeff Ronning began developing concepts for plug-in hybrids in the mid-1990s at then Delco Remy, Division of GM. EV1 prototypes were sometimes attached with "range-extender" trailers, developed by Alan Cocconi of AC Propulsion. These trailers were simply rolling gen sets that could supply power for long trips. It was only natural to conceive of an EV1 with a small turbo-alternator on board (1995 internal publication). External publications (SAE 971629 and 1999-01-2946) followed expounding the merits of using electrical energy for most local travel and proving it with the data from the US DOT. "Unlimited EV" and "Battery Dominant Hybrid" as well as "Energy Hybrid" were the given names for the architecture because the term "plug-in" hybrid coined by Dr. Andy Frank was considered at odds with Toyota's position that Prius did not need to be "plugged in" and their opinion that plugging was inconvenient. In 1997 (ten years before Volt), an internal project at the new spin-off, Delphi Corporation, began to convert an EV1 to a PHEV. However, the project was canceled by the corporate directors of technology.
In 1994, the Esoro H301 two-door, four passenger plug-in hybrid sedan was built in Switzerland by the vehicle prototyping company Esoro AG. Four such prototypes are still on the road. The lightweight (710 kg/1565 lb) vehicle featured a 360 cc engine in parallel with a 34 kW air-cooled AC induction motor. The 9 kWh nickel-cadmium battery could be recharged in four hours from a 220 V electrical wall outlet, or from 30% to 80% state of charge in about two hours at a steady speed of 120 km/h.
In 1998, Audi premiered a second iteration of the Duo plug-in hybrid, based on the Audi A4, at the Frankfurt Motor Show. The 1998 Audi Duo featured a parallel configuration similar to its predecessor. At the time, hybrid propulsion was considered as a promising solution to Europe's inner city emissions problems. Audi AG leased ten Duo PHEVs to Solarmobilverein Erlangen in the city of Erlangen, Bavaria as part of ELCIDIS (Electric Vehicle City Distribution), an advanced mobility project funded by the European Commission. Solar recharging stations were envisioned, but were not built. The fleet trial ended in August 2001.
About sixty 1998–1999 Audi Duo PHEVs were built. However, few customers were prepared to pay twice the price as the base model A4 equipped with an identical diesel engine, and series production was stopped.
2000–2005 2000 The Electric Power Research Institute (EPRI) sponsored the Hybrid Electric Vehicle Alliance to promote and develop original equipment manufacturer commercialization of plug-in hybrid electric vehicles. Alliance members include major automakers, national labs, utilities, and the University of California at Davis. EPRI's Hybrid Electric Vehicle Working Group published reports on PHEV attractiveness. Dr. Frank received new support from the European Commission, South Coast Air Quality Management District, Yolo-Solano Air Quality Management District, California Air Resources Board, and other governmental agencies.
2001 The U.S. Department of Energy created the National Center of Hybrid Excellence at UC Davis, with Dr. Frank as Director. Dr. Frank also obtained substantial GM funds to hybridize and plug-in GM's EV1. EPRI's Hybrid Electric Vehicle Working Group (HEVWG) published a report on costs and efficiencies of hybrid and plug-in hybrid vehicles. The report evaluated a small car, a midsize car, and an SUV, and simulated four powertrains for each vehicle: a conventional powertrain, a parallel HEV, a PHEV-20, and a PHEV-60.
Terminology note: A plug-in hybrid's all-electric range is designated by PHEV-(miles) or PHEV(kilometers)km representing the distance the vehicle can travel on battery power alone. For example, a PHEV-20 can travel 20 miles without using its internal combustion engine, or about 32 kilometers, so it may also be designated as PHEV32km.
2002 Entrepreneurs, environmentalists and engineers created the California Cars Initiative. CalCars is a non-profit PHEV advocacy and technology development group.
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'cite" electric-drive Kangoo battery electric van. The Elect'Road had a 150 km range using a nickel-cadmium battery pack and a 500 cc, 16 kW 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 V 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 litres and was housed within the right rear wheel arch. The range extender function was activated by a switch on the dashboard. The onboard 3.5 kW charger could charge a depleted battery pack to 95% SOC in about four hours from 220 volts. Passenger compartment heat was powered by the battery pack as well as an auxiliary coolant circuit that was heated by the range extender engine. Renault sold about 500, primarily in France, Norway and the UK, for about 25,000 euros each and redesigned the Elect'road in 2007.
With support from the South Coast Air Quality Management District, the California Air Resources Board, the National Renewable Energy Laboratory, the Electric Power Research Institute, and Volkswagen, Alan Cocconi of AC Propulsion converted a Volkswagen Jetta into a plug-in series hybrid. The engine was replaced with a 120 kW electric motor and 8.7 kWh’s worth of lead–acid batteries, which were charged by a trunk-mounted 1.4-liter internal combustion engine from a Volkswagen Lupo.
Professor Frank's vehicles were shown at the Paris International Auto Show and demonstrated to about 200 Renault engineers at its Paris headquarters. In the same year, Toyota shipped Coulomb, a University of California Davis Plug-in Hybrid Electric Vehicle, to Toyota City to demonstrate it to about 250 engineers and executives at two of Toyota's primary Tier 1 suppliers, Koyo Seiko, and Aisin AW (Aisin built the 1998–2003 Toyota Prius hybrid transaxle, as well as those used in the Ford Escape Hybrid, Toyota Camry Hybrid, and Nissan Altima Hybrid).
2004
In September, the California Cars Initiative converted a 2004 Toyota Prius into a prototype of what it calls the PRIUS+. With the addition of 130 kg (300 lb) of lead–acid batteries, the PRIUS+ achieved roughly double the gasoline mileage of a standard Prius and can make trips of up to 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.
Also in September, DaimlerChrysler displayed a plug-in hybrid version of its popular Mercedes-Benz Sprinter 311 CDI commercial van at the 2004 Internationale Automobil-Ausstellung Commercial Vehicle Show in Frankfurt, Germany. The diesel-engine PHEV Sprinters had a maximum all-electric range of 30 kilometers. Hand-built in Sindelfingen, Germany by Mercedes-Benz, the vehicles were tested around the clock, and some were placed in commercial fleet environments. The PHEV Sprinter's engine could be turned off by the driver for operation in historic European city centers that had outlawed internal-combustion engines.