Extended range electric vehicles combine a battery with a gas engine to reduce charging stops

An extended range electric vehicle (EREV) is a car that runs on battery power for everyday driving but has a small gas engine inside that kicks in when the battery runs low. You drive on electricity most of the time — for commutes, errands, short trips — and the gas engine generates power to extend your range when you need it. The gas engine does not directly turn the wheels the way it does in a hybrid; instead, it charges the battery while you drive.

The main difference between an EREV and a plug-in hybrid is how much electric-only range they offer. An EREV is built around the battery first, with the gas engine as a backup. A plug-in hybrid is built around the gas engine first, with the battery as an add-on. In practice, this means an EREV can handle most of your weekly driving on electricity alone, while a plug-in hybrid is designed to switch between gas and electric more often.

Key Takeaways

  • Extended range electric vehicles run on battery power for daily driving and use a gas engine to generate electricity when the battery is depleted, so you rarely need to charge at home if you have access to public charging.
  • You plug in an EREV at home or at a public charger, just like a battery electric vehicle, but the onboard gas engine means you can complete longer trips without finding a charger.
  • The gas engine in an EREV does not power the wheels directly; it only generates electricity, which is why the car can run silently on battery power most of the time.
  • EREVs produce lower emissions than gas-only cars because they use electricity for most trips, but they produce more emissions than battery electric vehicles over their lifetime.

How the battery and gas engine work together

When you start an EREV, the battery powers the electric motor. As long as the battery has charge, the car runs silently on electricity alone. You drive normally — accelerating, braking, merging — and the battery supplies all the power. The gas engine stays off.

When the battery charge drops to a set level (usually around 20 to 30 percent), the gas engine turns on automatically. It does not shift the car into gear or move the wheels. Instead, it runs a generator that produces electricity, which charges the battery while you drive. You may notice the engine sound, but the wheels are still being turned by the electric motor, powered by the battery that the gas engine is now recharging. Once the battery reaches a higher charge level, the gas engine shuts off again.

This design means you can drive an EREV for weeks without using the gas engine if your trips are short enough to fit within the battery's range. A typical EREV has 20 to 50 miles of electric-only range, depending on the model and battery size. If you drive 30 miles a day and charge at home every night, you may never need the gas engine. If you take a 200-mile road trip, the gas engine will run for part of the journey.

Charging an EREV at home and on the road

You charge an EREV the same way you charge a battery electric vehicle: by plugging it into a wall outlet or a dedicated charger. A standard 120-volt household outlet charges slowly — usually adding 2 to 5 miles of range per hour. A 240-volt home charger (the kind used for electric water heaters) charges much faster, typically adding 20 to 30 miles of range per hour, depending on the car's battery size.

Most EREV owners install a 240-volt charger at home and plug in overnight. A full charge usually takes 4 to 10 hours, depending on the charger and battery size. If you do not have a home charger, you can use public charging stations, though charging away from home is slower and less convenient than charging at home.

Because an EREV has a gas tank, you also have the option to refuel with gasoline at any gas station. This is the safety net that makes EREVs practical for people who cannot install a home charger or who take frequent long trips. You can drive across the country without worrying about finding enough charging stations.

Emissions and environmental impact

An EREV produces lower emissions than a gas-only car because it uses electricity for most driving. If your electricity comes from renewable sources like wind or solar, the emissions are even lower. However, an EREV produces more emissions over its lifetime than a battery electric vehicle, because the gas engine does produce emissions when it runs, and manufacturing the battery and gas engine together uses more resources than manufacturing a battery alone.

The environmental benefit of an EREV depends on how you drive it. If you charge regularly and take mostly short trips, you will use the gas engine rarely, and your emissions will be close to those of a battery electric vehicle. If you take long trips frequently and rarely charge, you will use the gas engine often, and your emissions will be closer to those of a plug-in hybrid or a gas car.

The electricity grid in your region also matters. In areas where electricity comes mostly from coal or natural gas, the emissions benefit of an EREV is smaller than in areas where electricity comes mostly from renewables or nuclear power. Over time, as electricity grids shift toward renewable sources, the emissions benefit of owning an EREV will increase.

Cost of buying and owning an EREV

An EREV costs more upfront than a comparable gas car, usually $5,000 to $15,000 more, depending on the model and battery size. This price difference reflects the cost of the battery and electric motor. However, EREVs often cost less than battery electric vehicles because they have a smaller battery and do not require as much charging infrastructure to be practical.

Operating costs are lower than a gas car because electricity is cheaper than gasoline per mile driven. Maintenance costs are also lower because electric motors have fewer moving parts than gas engines and require less routine service. You will still need oil changes and other maintenance for the gas engine, but less frequently than in a gas-only car.

Some states and the federal government offer tax credits or rebates for purchasing an EREV, though the amount and availability vary by location and change over time. Check your state's environmental agency or the federal government's energy website for current incentives in your area.

EREV models currently available

The Chevrolet Volt is the most common EREV sold in the United States. It has about 50 miles of electric-only range and a gas engine that extends total range to over 400 miles. The BMW i3 with range extender is another option, offering about 40 miles of electric range plus a small gas engine.

Some manufacturers have shifted away from EREVs toward battery electric vehicles or plug-in hybrids, so the selection is smaller than it was a few years ago. If you are considering an EREV, research current models and their availability in your region, as the market changes frequently.

When an EREV makes sense for your situation

An EREV is a good fit if you have a home charger or access to regular charging, take mostly short trips, and occasionally need to drive long distances without stopping to charge. It is also practical if you live in an area with limited public charging infrastructure but want to reduce your gas consumption.

An EREV may not be the best choice if you cannot install a home charger and do not have regular access to public charging, because you will end up using the gas engine frequently and lose the environmental and cost benefits. It is also less practical if you take very long trips regularly, because you will spend time waiting for the gas engine to generate enough charge, rather than straightforward refueling at a gas station.

If you drive mostly short trips and have a home charger, a battery electric vehicle may be a better choice because it eliminates the gas engine entirely and has lower lifetime emissions. If you take long trips frequently and cannot charge at home, a gas car or a plug-in hybrid may be more practical.

Frequently Asked Questions

Do I have to plug in an EREV every day?

No, but you should plug in regularly to get the most benefit from the battery. If you do not plug in, the gas engine will run more often, and you will lose the cost and emissions savings. Most owners plug in at home overnight, but you can go weeks without charging if your daily trips are short enough to fit within the battery range.

Can I drive an EREV on the highway without charging?

Yes. Once the battery depletes, the gas engine turns on and generates electricity to power the motor. You can drive across the country on gas alone if you need to, though the gas engine will run continuously on long highway trips, which uses more fuel than it would on short trips.

What happens if the battery dies while I am driving?

The gas engine automatically turns on and generates electricity to keep the car moving. You will not be stranded. The car will continue to run on the gas engine until you can charge the battery or refuel with gasoline.

Is an EREV cheaper to own than a gas car?

Over time, yes, if you charge regularly. Electricity costs less per mile than gasoline, and maintenance is lower because the electric motor has fewer moving parts. However, the upfront purchase price is higher, so the payback period depends on how much you drive and how often you charge.

How long does it take to charge an EREV at a public charging station?

It depends on the charger type. A Level 2 charger (240 volts) typically adds 20 to 30 miles of range per hour. A DC fast charger can add 100 miles in 20 to 30 minutes, though charging speed slows as the battery fills. Most public chargers are Level 2, which takes 4 to 8 hours for a full charge.