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Frequently Asked Questions :: Hybrid Vehicles

(primary source: U.S. DOE, Clean Cities Program)

Q: What is a hybrid electric vehicle

A:Hybrid electric vehicles (HEVs) typically combine the internal combustion engine of a conventional vehicle with the battery and electric motor of an electric vehicle . The combination offers low emissions, with the power, range, and convenient fueling of conventional (gasoline and diesel) vehicles—and HEVs never need to be plugged in.

Hybrid electric vehicles of the future could use alternative fuels such as biodiesel , natural gas , or ethanol . The flexibility of HEVs makes them well suited for fleet and personal transportation. Learn more about the components of a hybrid system .

Hybrid electric vehicles currently do not qualify as alternative fuel vehicles under the Energy Policy Act of 1992 . However, they do qualify for incentives and provide several important benefits . Learn about currently available HEVs .

How Hybrid Electric Vehicles Work

Hybrid electric vehicles are powered by two energy sources—an energy conversion unit (such as an internal combustion engine or fuel cell) and an energy storage device (such as batteries or ultracapacitors). The energy conversion unit can be powered by gasoline, diesel, compressed natural gas, hydrogen, or other fuels.

Hybrid electric vehicles have the potential to be two to three times more fuel-efficient than conventional vehicles. HEVs can have a parallel design , a series design , or a combination of the two.

Q: How do HEVs perform and compare to conventional vehicles in terms of mileage, fuel use, safety, greenhouse gas emissions, etc?

A: HEVs either meet or exceed conventional vehicle performance characteristics and perform similarly to gasoline vehicles.

The Fuel Economy Website is a comprehensive resource for all automobiles, including the newest hybrids. Click on "Find a Car" and use the pull-down menus to select the automobile you are interested in. It gives complete information on annual fuel costs, mileage, greenhouse gas emissions, air pollution ratings, safety studies, and more.

Q: What tax incentives or rebates are available to me for purchasing an HEV?

A: Hybrids purchased or placed into service after December 31, 2005, may be eligible for a federal income tax credit of up to $3,400. Credit amounts begin to phase out for a given manufacturer once it has sold over 60,000 eligible vehicles. For more information, see

Also see the Fuel Efficient Vehicle Tax Incentives Information Center for information on electric vehicles and alternative fuel vehicles.

Addtional information is available at Database of State Incentives for Renewables & Efficiency, a comprehensive source of information on state, local, utility, and federal incentives that promote renewable energy and energy efficiency.

Q: Is an HEV simply a transition vehicle between a conventional vehicle and a pure EV?

A: No. Most experts agree that the car of the future will be an HEV of some kind. Because the energy density of electric batteries will never equal that of liquid or gaseous fuels, these fuels will likely need to continue to be a part of future vehicles. Even fuel cells, which are a promising long-term technology for personal transportation, will most likely still be put into an HEV configuration with a high-power energy-storage/buffer device on board. With further development, we might get to the point where we can select the propulsion system on our HEV in the same way we select a 4-cylinder engine or a V8 today.

Q: What is the life expectancy of HEV batteries, and what are the costs associated with replacing them?

A: Most warranties for HEV batteries typically cover a driving range from 80,000 to 100,000 miles, depending on the manufacturer. Therefore, costs associated with replacing the battery depend on the warranty and time elapsed. For a new battery not under any warranty, costs can range from $3,000 to $8,000. For specific details check with the HEV manufacturer.

Q: My primary interest in buying an HEV is in doing my part to clean up the air. Can my decision to purchase an HEV now really make a difference?

A: Yes. Conventional vehicles release harmful chemicals, or pollutants, through their tailpipes. These chemicals, such as oxides of nitrogen, volatile organic compounds, particulates, carbon monoxide, and carbon dioxide, are produced through the combustion of fossil fuels. In addition to causing "smog," and possibly contributing to global warming, these chemicals have been determined to cause or aggravate human respiratory diseases, including bronchitis, emphysema, pulmonary fibrosis, and asthma. HEVs, with their increased fuel economy and reduced use of fossil fuels, emit fewer of these pollutants into the air we breathe. And because every little bit helps, your decision to purchase a cleaner vehicle now can have a big impact on the quality of our air in the future.

Q: Where can I find ratings of hybrid vehicles?

A: The American Council for an Energy-Efficient Economy's (ACEEE) Green Book ® is a valuable resource for comparing fuel-efficiency and other features of passenger vehicles. For a table showing a simple hybrid comparison, see

Another useful resource is the Federal Fuel Economy Guide website.

Q: How do hybrid batteries re-charge? Do I need to plug a hybrid in?

A:The batteries recharge by reclaiming energy when the car brakes. Many industry observers expect some future hybrids to be "plug-in hybrids," offering the option to recharge more powerful batteries via a common household electric socket, while still maintaining a small gasoline engine. (Source:

Q: Is it expensive to replace hybrid batteries?

The hybrid battery packs are designed to last for the lifetime of the vehicle, somewhere between 150,000 and 200,000 miles, probably a whole lot longer. The warranty covers the batteries for between eight and ten years, depending on the carmaker.

Battery toxicity is a concern, although today's hybrids use NiMH batteries, not the environmentally problematic rechargeable nickel cadmium. "Nickel metal hydride batteries are benign. They can be fully recycled," says Ron Cogan, editor of the Green Car Journal. Toyota and Honda say that they will recycle dead batteries and that disposal will pose no toxic hazards. Toyota puts a phone number on each battery, and they pay a $200 "bounty" for each battery to help ensure that it will be properly recycled.

There's no definitive word on replacement costs because they are almost never replaced. According to Toyota, since the Prius first went on sale in 2000, they have not replaced a single battery for wear and tear. (Source:

Q: What are the main characteristics of an HEV compared to a conventional car?

Some of main characteristics that differentiate a hybrid car from a conventional car are:

• Fuel Economy - hybrid cars offer greater fuel economy

• Cleaner - hybrid cars emit less emissions

• Battery powered - hybrid cars combine an internal combustion engine with a battery

• Smaller ICE - hybrid cars have smaller engines than conventional car

• Regenerative Braking - The batteries recharge themselves during braking, unlike an electric car, the hybrid car does not need to be plugged in.

• Automatic Start/Shutoff - In hybrid cars the engine automatically shuts off when the vehicle comes to a stop. The motor starts automatically restarts when the accelerator is pressed. (source: Hybrid Car FAQ)

Can I convert a gasoline-powered vehicle to an electric vehicle?

The cost of converting a gasoline-powered vehicle to an electric vehicle can be high. Electric cars can run on either alternating current (AC) or direct current (DC). If the motor is an AC motor, it will probably be a three-phase AC motor running at 240 volts AC with a 300-volt battery pack. A DC motor may run on anything from 96 to 192 volts.

DC installations tend to be simpler and less expensive. For a typical DC system conversion, the cost will be $6,000 to $10,000 for parts, including a motor ($1,000 to $2,000), controller ($1,000 to $2,000), adapter plate ($500 to $1,000), and batteries ($1,000 to $2,000), plus $3,500 to $8,000 for labor. AC system conversion will cost $10,000 or more for parts and $2,000 or more for batteries for these higher-voltage systems. The cost of conversion can be partially offset by lower operating costs. See the discussion of operating costs under What is an Electric Vehicle? Because conversion to all-electric power does not require U.S. Environmental Protection Agency certification, conversions are often performed by amateur mechanics and high school and college automotive training facilities.

The most popular vehicles for electric conversion are vehicles with manual transmissions, including the Volkswagen Rabbit, Porsche 914, Honda Civic, Honda CRX, Ford Escort, and air-cooled Volkswagens. For more information about general alternative fuel vehicle conversions, go to DOE's Conversions page.

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