Study: how hot summer affects your EV’s range

As is commonly known, freezing cold temperatures affect an EV’s range. But how do extreme summer temperatures affect its battery capacity?

When temperatures rise to 38 degrees Celcius, like in Southern Europe, that can shorten your range by 31%, an ongoing study by American Recurrent Motors Inc. shows, using data from 7,500 live connected cars.

No dramatic losses up to 32°C

Still, it isn’t as dramatic as it looks at first sight and is less than in winter. Recurrent analysts say it all comes down to how you heat up or cool down the car’s interior. By 24°C, there is no loss, for instance, and at 32°C, it is only 5%.

Recurrent use data from a fleet of 7,500 EV owners in the US connected through an app. It pings the car’s battery state three times a day and gathers the data in a central database. In return, the owner gets detailed reports of how his EV battery performs or degrades by age.

Chemical process

That data shows that range loss becomes exponential only above a specific temperature. The built-in battery management system protects the batteries from extreme heat.

Batteries delivering electricity are merely a chemical process, more affected by cold than heat, with the viscosity of the liquids used as electrolytes affecting it.

Recurrent warns that “letting an EV fall to extremely low states of charge can be risky in the summer because a car’s thermal management requires energy. Keep the battery charged; it will keep the battery cool.”

“That doesn’t mean you can’t leave your car in the airport parking lot for a week, but it is something to consider if you live in a scorching climate.”

Air conditioning

Putting the blame where it belongs, Recurrent points at the air conditioning, which needs energy to cool down the car’s interior. However, cooling your EV’s cabin will be less range-intensive than heating it in winter.

Using your A/C during normal summer conditions should not significantly reduce the EV range. But when it gets really hot, the A/C has to work harder, especially for the initial cooling-down.

It may take 3-5 kW of energy to get a 35°C car to a comfortable temperature, but it takes only around 1 kW to keep it at 21 degrees. So, the general advice is to let your EV cool down while it is still plugged in. Most EVs let you do that even remotely using the car’s dedicated app.

Needing less energy than an ICE car

In fact, the A/C in an EV uses less energy than in a classic combustion engine car. “With a gas car, the engine produces a lot of waste heat that the air conditioner must also fight against to keep the cabin cool.”

“An EV does not produce the same amount of heat when running, so the AC doesn’t have to work as hard.” One advantage of the EV’s A/C is that cold air is available immediately. There is no more waiting for the air compressor to kick in as the engine warms up.

On the downside, in winter, an ICE car uses the wasted heat to warm up the interior; an EV needs a warming element like a resistance heater or (often optional) heat pump.