EREVs are vehicles that have a gas generator that can be used as a source of power for an electric drive train. That is, the wheels are driven by an electric motor, like a “regular” (battery) electric vehicle, but instead of the energy coming from a battery that was charged by plugging the car in, the the energy can also come from the vehicle’s gas-powered generator (via the battery).
What’s the difference between an EREV and a hybrid electric vehicle?
Both a EREV and a hybrid electric vehicle have:
- An electric motor,
- A gas-powered engine or generator, and
- A battery,
but…
- In a hybrid electric vehicle, both the gas engine the electric motor can directly contribute to turning the wheels of the car.
- In a EREV, only an electric motor turns the wheels. The gas “engine” is actually a generator and only indirectly contributes to turning the wheels by generating electricity for the electric motor (usually by charging the battery used by the motor).
What’s the difference between an EREV and a battery electric vehicle (BEV)?
Both EREVs and BEVs have:
- An electric motor and
- A battery,
but…
- In a BEV, the only way the battery gets energy is by plugging it in (and some through regenerative braking). The battery has to be very large (and thus adds a lot of weight) in order for the vehicle to have a reasonable range (about 250+ miles) to reduce the need to stop to plug in.
- EREVs will most likely have a battery, but a much smaller one (perhaps with a range of about 50-150 miles)¹ — which also means a lot less battery weight than a BEV. The generator runs as needed to charge the battery (and possibly to supplement power from the battery to the motor).
EREVs are likely also able to be plugged in. That means that short drives can be powered mostly or even exclusively using energy in the battery that came from plug-in charging (which can come from clean energy sources).
¹ EREVs are only beginning to launch in the U.S. market, so there is no “typical” battery size of an EREV, yet.
Plug-in EREVs can make a lot of sense, for now
Battery Electric Vehicles (BEVs) aren’t without compromises or drawbacks (some of which are more perceived than actual). Here’s how EREVs address those:
- Range: EREVs have the capability of a much longer range than BEVs, including while towing.
- Charging not required: An EREV has the convenience of fast, prevalent, familiar refueling that is important to many people.
- Convenience & Familiarity: Charging stations are not nearly as ubiquitous as gas stations, and charging takes longer. EREVs allow people to fill up quickly and conveniently, in a way they are familiar with.
Of course, using gas to power a car has drawbacks, too, but…
EREVs are still a step in the right direction
- Efficiency and climate impact that’s better than gas/hybrid vehicles (and can be nearly as good as BEVs)…
- The generator can run only at maximum efficiency. Gas engines/generators are less efficient at lower speeds, but a generator for an EREV should be designed to only run at the speed it’s most efficient at — that is, even using only gas, and EREV should have lower pollution output per mile than traditional and hybrid ICE cars. Related…
- It’s possible that many trips/miles could be powered just by energy supplied by plugging the car in.
- For those who will plug it in regularly, many miles driven could be powered from cleaner energy supplies (whether from their own residential solar or the grid). When we had a plug-in hybrid with just 10 miles of battery-only range, still more than half the miles we drove were powered from plug-in charging.
- Introduction to EV performance and usage. All of these attributes can help ease people into the world of EVs.
- Get used to charging instead of refueling.
- Learn how great an electric powertrain can be (e.g., instant torque) and the other benefits of having a somewhat large battery in the car (lots of power for tools, tailgate parties, camping, etc).
In other words, this is a reasonable solution while we continue the long transition to EVs…
A transition technology
EVs and the ecosystem around it are actively being improved, such as:
- Cheaper batteries, which would make BEVs more cost competitive.
- Higher capacity batteries, which can increase the range of BEVs.
- Lighter batteries, which would reduce the weight and increase the range and efficiency of BEVs (and/or reduce their cost).
- Better cold weather performance batteries.
- Safer batteries that are less likely to experience thermal runaway — battery fires that are difficult to put out.
- Faster charging, so people don’t have to wait around substantially longer than refueling.
- More charging stations with higher reliability with better amenities, so charging on-the-go is less unpleasant and unpredictable.
- More charging options, such a charging in apartment shared garages and curbside charging posts.
Industries — battery tech, charging infra, etc. — are actively working on these and making great progress, but it will be many years before we’re in a great place for all of these. In the meantime, it’s fair that some people aren’t able or willing to accept the compromises of BEVs, and EREVs offer a middle ground option.
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