A hybrid car pairs a gasoline engine with one or more electric motors that run on a battery. The motor helps the engine use less fuel, and in some models it can drive the car by itself. What separates one kind of hybrid from another is the size of the battery and whether you have to plug the car in.
How a hybrid works
According to the U.S. Department of Energy, a hybrid electric vehicle combines an internal combustion engine with electric motors that draw power from a battery. The extra power from the motor can allow a smaller engine, and the battery can run accessories and reduce idling when the car is stopped.
The battery gets recharged in two ways. The engine can generate electricity, and regenerative braking captures energy when you slow down. During braking, the electric motor acts as a generator and stores energy that would otherwise be lost as heat.
Most hybrids use a parallel design, where the engine and the electric motor both connect to the wheels mechanically. In a series design, only the motor turns the wheels and the engine’s job is to make electricity. The Department of Energy says series setups are more common in plug-in hybrids.
The three types of hybrid
Mild hybrid
Also called a micro hybrid, it uses a small battery and motor to assist the engine. It can shut the engine off when you’re stopped, but it can’t drive on electricity alone. Mild hybrids generally cost less than full hybrids and save less fuel.
Full hybrid
A full hybrid has a larger battery and stronger motors. It can drive short distances at low speeds on electricity alone, switching between engine and motor automatically. It costs more than a mild hybrid but delivers a bigger fuel economy benefit. A full hybrid cannot be plugged in: the battery charges only from the engine and regenerative braking.
Plug-in hybrid (PHEV)
A plug-in hybrid carries a larger battery pack that can charge from an outside power source, as well as from the engine and regenerative braking. The Department of Energy says current plug-ins can drive about 15 to 60-plus miles on electricity alone, which is called the electric range. After that, the engine takes over.
Quick comparison
| Mild hybrid | Full hybrid | Plug-in hybrid | |
|---|---|---|---|
| Drives on electricity alone | No | Short distances, low speeds | About 15 to 60+ miles |
| Plugs in | No | No | Yes |
| Battery | Small | Larger than mild | Largest of the three |
| Fuel savings | Smallest | Medium | Largest, if you plug in |
Do I have to plug in a hybrid?
Only a plug-in hybrid. Mild and full hybrids never need a cable. The Department of Energy points out that a plug-in that is never plugged in gets about the same fuel economy as a similarly sized regular hybrid, so you lose its main advantage. Consistent charging is the best way to get the most from one, and even plugging in between short trips can allow all-electric driving.
For many people the pattern looks like this: drive to work on electricity, plug in overnight, and use the engine only on longer trips. The engine also kicks in when the battery is mostly depleted, during rapid acceleration, or when heating or air conditioning loads are high.
Which hybrid fits you
- You can’t charge at home or work: a full hybrid (or a mild hybrid if you’re on a tighter budget) saves fuel without changing how you fill up.
- You have a garage outlet or a charger nearby and drive short distances: a plug-in lets you do most of your daily driving on electricity.
- You’re curious about going fully electric: a plug-in is a middle step, since you charge it like an EV but still have the engine as a backup for road trips. If you’re weighing the full jump, read our take on whether electric cars are worth it.
What to watch out for
Hybrids often cost more than comparable gasoline-only cars, and plug-ins generally cost more than similar conventional and hybrid models. The Department of Energy says fuel savings or state incentives can offset part of that difference. FuelEconomy.gov has a tool called “Can a Hybrid Save Me Money?” that compares a hybrid with a similar non-hybrid.
For plug-ins, emissions may be lower, depending on the electricity source and how often the car runs in all-electric mode. It’s part of a bigger shift away from gas, which we covered in gas cars falling below 50% of global sales.
Frequently asked questions
Do hybrid cars need to be plugged in?
Only plug-in hybrids do. Mild and full hybrids recharge on their own through regenerative braking and the engine.
Can a hybrid drive on electricity only?
A full hybrid can for short distances at low speeds. A plug-in can go roughly 15 to 60-plus miles. A mild hybrid can’t drive on electricity alone.
What happens when a plug-in’s battery runs out?
The engine takes over, so you’re never stranded. Fuel economy then drops to about that of a regular hybrid.
Hybrid or EV: which should I pick?
If you can’t charge regularly, a hybrid is the more practical choice. If you have easy home charging and drive a lot, a fully electric car may save you more.
