Electric vehicles (EVs), research has consistently shown, produce fewer climate-warming emissions compared to cars that burn gasoline or diesel. But could hybrid vehicles be a better deal for the climate than full EVs? “You can construct those cases and get that answer,” says Sergey Paltsev, deputy director of the MIT Center for Sustainability Science and Strategy and senior research scientist at the MIT Energy Initiative. However, it might require cherry-picking data to find a very specific set of circumstances.

There are two types of hybrid vehicles, both of which run on a mix of electricity from a battery (like an EV) and a gasoline engine (like an ordinary car). A traditional hybrid vehicle, like a Toyota Prius, carries a battery that recharges while the car’s engine runs. This energy is delivered to the wheels through electric motors, allowing the car to switch quickly between electric and gas power depending on driving conditions. A plug-in hybrid vehicle (PHEV), meanwhile, is essentially a full EV with a gas engine as a backup. This allows it to get by with a much smaller battery than a pure EV: when the battery runs out, the gas engine takes over.

No matter the vehicle, driving on gasoline virtually always does more to affect the climate than driving on battery power. That’s partly because burning gasoline in an engine directly produces climate-warming carbon dioxide (CO2). But it’s also because electric motors are much more efficient than engines at turning energy into driving power. For example, consider an EV charged in West Virginia, where most electricity comes from burning coal—itself a major source of CO2. This car still produces less CO2 per mile driven than a gas-powered car, because it gets so much mileage out of every bit of electricity in its battery.

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