How Do Electric Cars Work?

What are the main parts of a battery-electric car?

A battery-electric vehicle (BEV), also called an all-electric vehicle, has an electric motor instead of an internal combustion engine.^[1] A large traction battery pack powers the motor, and the car must be plugged in to a wall outlet or to charging equipment.^[1] Because it runs on electricity, it emits no tailpipe exhaust and has no fuel pump, fuel line or fuel tank.^[1]

The U.S. Department of Energy's Alternative Fuels Data Center (AFDC) lists these key components.^[1]

How does energy flow from the plug to the wheels?

When the car is plugged in, the onboard charger converts alternating current (AC) from the grid into direct current (DC) for the battery and monitors the battery's voltage, current, temperature and state of charge.^[1] Some energy is lost in this conversion and in overcoming the battery's resistance to charging, which rises as the battery fills up.^[6]

When the car moves, the power electronics controller manages the energy flowing out of the battery, controlling the motor's speed and the torque it produces.^[1] The motor turns the wheels through the transmission.^[1] The DC/DC converter supplies lower-voltage power for accessories and recharges the auxiliary battery.^[1]

According to fueleconomy.gov, an EV's electric drive system accounts for only a 15% to 20% energy loss, compared with 64% to 75% for a gasoline engine.^[6] The motor also stops when the car stops, so no energy is wasted idling.^[6]

What is regenerative braking?

When a driver brakes in a conventional car, the energy that was used to get it moving is lost as heat through friction at the brakes.^[6] Electric cars recover some of that energy instead.^[6] Braking lets the vehicle's inertia turn an electric motor-generator, which produces electricity that is stored in the battery and can later power the motor again.^[6]

Because there is more braking in stop-and-go traffic, electric cars are most efficient in city driving.^[6] On the highway, where there is little braking, regenerative braking gives little advantage over a conventional vehicle.^[6]

How are battery-electric, plug-in hybrid and hybrid cars different?

All three types use electricity and are sometimes loosely called electric vehicles, even though some still use liquid fuels.^[2]

A plug-in hybrid has a larger battery than a hybrid, so it can drive a moderate distance on electricity alone.^[3] Its engine takes over when the battery is mostly depleted, during rapid acceleration or when heating or air-conditioning loads are heavy.^[3] AFDC pages, as checked in October 2026, give different figures for this electric range: about 15 to 60-plus miles in current models on one page, and 20 to 40 miles for most plug-in hybrids on another.^[3][2] A regular hybrid cannot be plugged in, and the extra power from its electric motor can potentially allow a smaller engine.^[8]

How long does it take to charge an electric car?

Charging equipment is classified by how fast it charges the battery.^[4] Times depend on the battery's size, type and state of charge, the car's internal charger and the equipment, and can range from less than 20 minutes with DC fast chargers to 20 hours or more with Level 1.^[4]

Most EVs come with a portable Level 1 cord, and 8 hours of Level 1 charging can add about 40 miles of range to a mid-size EV.^[4] Level 2 equipment can charge a typical EV battery overnight, and all commercially available EVs in the United States can use both Level 1 and Level 2.^[4] DC fast charging, also called Level 3, serves heavy traffic corridors, and its charging power varies with the vehicle and the battery's state of charge.^[4]

Are electric cars more efficient than gasoline cars?

According to fueleconomy.gov, EVs convert over 77% of the electrical energy from the grid into power at the wheels, while conventional gasoline (petrol) vehicles convert only about 12% to 30% of the energy stored in their fuel.^[5]

Another fueleconomy.gov page gives different figures: 60% to 66% of an EV's energy reaches the wheels in city driving and 71% to 73% on the highway, or more than 94% in the city and 77% on the highway if energy reused through regenerative braking is counted.^[6] That page says its energy-flow estimates are based primarily on a 2012 Nissan Leaf.^[6] An EV must provide all its cabin heat from electricity, and in very cold conditions auxiliary electrical loads can account for more than 40% of energy use in city driving.^[6]

The Environmental Protection Agency (EPA) explains that an EV's fuel economy is given in miles per gallon of gasoline-equivalent (MPGe): how far it can go on an amount of electricity with the same energy content as a gallon of gasoline.^[7] This allows an EV to be compared with a gasoline vehicle.^[7]