Driving an electric car in summer, and what 40 degrees really costs you

How much range does an EV lose in the heat?

Less than you expect, and far less than cold weather takes. An electric car in summer gives up single-digit percentages on a warm day, and the loss only becomes obvious once the outside temperature pushes past the mid-30s.

US analytics firm Recurrent, drawing on data from about 30,000 electric vehicles, found cars lose roughly 5 per cent of their range at 32 degrees and 17 to 18 per cent at 37 degrees, according to its research on what air conditioning does to range. Those figures are American, so treat them as the shape of the curve rather than a local guarantee.

The Australian number is smaller. In advice published in January 2025, RACV said that on days above 35 degrees an EV’s cooling system draws extra energy to protect the battery pack, which can cut range by up to 10 per cent. RACV also puts the battery’s happy zone at 15 to 35 degrees, with around 22 degrees as ideal.

Heat is the smaller of the two temperature problems. Geotab’s 2023 analysis of real-world trips found range peaks at about 20 degrees outside, where cars averaged around 15 per cent better than their rated range, and that extreme cold can take as much as 50 per cent. A 37-degree day costs you under 20 per cent. A freezing one can cost you half the car.

Put the Geotab and Recurrent measurements side by side and the pattern is clear.

Outside temperature	Effect on range	Measured by
20°C	About 15% better than rated range	Geotab, 2023
32°C	About 5% lost	Recurrent
35°C and above	Up to 10% lost	RACV
37°C	17% to 18% lost	Recurrent

Should I charge my EV differently in summer?

Yes, but the change is timing rather than technique. Charge overnight or early in the morning instead of in the middle of a hot afternoon, and the car spends less energy cooling itself while it fills.

Australian charging network Evie Networks tells drivers to avoid the hottest part of the day and charge early morning or later in the evening, and puts the battery’s best working window at roughly 20 to 30 degrees. RACV makes the same point for a practical reason: charging overnight or in the shade means less active thermal management, which means less electricity used for the same kilometres.

On state of charge, which is simply how full the battery is as a percentage, Evie Networks recommends staying between 20 and 80 per cent for daily driving rather than topping up to 100 per cent out of habit. Recurrent adds a summer-specific twist and suggests keeping the car above 50 per cent in very hot weather, so the pack always has energy available to run its own cooling.

The habit worth breaking is leaning on public DC fast chargers all summer because they are quick. Geotab’s battery health analysis found cars that frequently used chargers above 100kW degraded at 3.0 per cent a year, double the 1.5 per cent a year measured on cars that rarely fast-charged. Occasional road-trip charging is not the problem. Doing it every week when a home socket would do is.

If you drive a Tesla, RACV notes that models including the Model 3 and Model Y warm or cool the pack to the right charging temperature automatically once you set a Supercharger as your destination. Other brands offer similar preconditioning, and it is worth finding the setting before a hot long weekend rather than in a queue at a highway charger.

Is Australian heat damaging my battery?

Slightly, and much less than the internet suggests. Sustained heat does accelerate battery ageing, but the measured difference is small enough that it should not change how you use the car.

Geotab’s study of more than 22,700 electric vehicles across 21 models put average degradation at 2.3 per cent a year, and found cars in hot climates lose 0.4 percentage points a year more than those in mild ones. At the average rate, a pack still holds about 81.6 per cent of its original capacity after eight years. The hot-climate penalty over that period is a few percentage points, not a cliff.

The reason is active thermal management, the liquid cooling loop that keeps the pack in its working range. “EV batteries could start to see an increase in battery degradation if they exceed 55°C, but this would very rarely happen with active thermal management”, says Rohan Smith, product manager for electric vehicles at RACV. Smith also points out that EVs are less likely to overheat than petrol cars, because an electric motor generates far less waste heat than an engine.

The exception is worth knowing before you buy rather than after. RACV notes that some models, the Nissan Leaf among them, use passive cooling only, relying on fans and ambient air rather than a cooling circuit. In a Darwin or Mildura summer that matters. Check which system a used EV has before you sign.

What actually saves range on a 40-degree day?

Slowing down. Speed costs an electric car more range in hot weather than the air conditioning ever will, and it is the one lever most drivers ignore.

Analysing more than three million trips, Geotab found that a 65kWh electric van running its aircon at 30 degrees lost 39 per cent of its range as speed rose from 80km/h to 129km/h. Dropping from 113km/h to 97km/h on the highway gives back 10 to 20 per cent. Nothing you do with the climate control comes close to that.

Drivers tend to worry about using the aircon in hot weather, but our data shows that your right foot can make the biggest difference.

Charlotte Argue, senior manager of sustainability, Geotab

After that, four things are worth doing on a hot day.

• Pre-cool the cabin from your phone while the car is still plugged in, so the grid pays for pulling the temperature down instead of the battery.
• Use ventilated seats and the fan on your side rather than chilling the whole cabin, which Geotab recommends as a cheaper way to stay comfortable.
• Park in shade or under cover where you can, which Evie Networks lists alongside pre-cooling as its main summer advice.
• Keep the car’s software current, because manufacturer updates often change how the thermal management behaves.

Best for anyone facing a run of 40-degree days: charge at home overnight on a timer and pre-cool the cabin on the charger before you unplug. That combination handles the heat and the range loss at the same time, with no change to how you drive.

One thing is not an EV question at all. RACV testing published in January 2024 found vehicle interiors can pass 70 degrees within minutes when it is only 30 degrees outside, and its roadside team took 664 calls to free children locked in cars during 2023. Some EVs can keep the climate control running while parked. Never treat that as a reason to leave a child or a pet in the car.

The short version of an Australian summer in an electric car: expect to lose a bit of range above 35 degrees, shift your charging to the cool hours, ease off on the freeway, and stop worrying about the battery. The heat is doing much less to it than you think.