How hot or cold weather affects electric car range

Electric vehicles (EVs) differ from gas-powered ones in lots of obvious ways, but one of the less obvious differences is how their driving range is affected by extreme temperatures. All vehicles lose range in very hot or very cold weather—it takes more gasoline to run the air conditioner on high or heat up a cold car by idling, after all—but thanks to circumstances of battery chemistry and engineering, EVs are especially affected. That doesn't mean they can't be driven in adverse weather, just that EV owners should take a few precautions and plan ahead to avoid unexpected drops in driving range. We look at how much EVs are affected by external temperatures, why it happens, and what you can do about it. 
Measuring EV range in extreme weather

 

To find out how much of an impact extreme weather has on driving range, AAA tested five electric vehicles, all with a minimum EPA estimated driving range of 100 miles, in partnership with the Automobile Club of Southern California’s Automotive Research Center. Real-world driving conditions were simulated using a dynamometer, essentially a treadmill for cars, in a closed testing cell where ambient temperature could be closely controlled. To determine the effects on driving range, scenarios for cold and hot weather conditions – both when using climate control and not – were compared to those of driving with an outside temperature of 75°F. 
Chevy Bolt EV being range-tested

The results

When climate control wasn't in use, estimated driving range for electric vehicles was moderately impacted by hot and cold temperatures when compared to testing conducted at 75°F. Climate control use resulted in considerable reductions in driving range.

  • 20°F

    20°F

    -12% decrease
    in driving range
  • 20°F with heater on

    20°F with heater on

    -41% decrease 
    in driving range
  • 95°F

    95°F

    -4% decrease 
    in driving range
  • 95°F with A/C on

    95°F with A/C on

    -17% decrease 
    in driving range

These results mean that on average, for every 100 miles an EV can drive at 75°F, it can drive 83 miles at 95°F with the air conditioning on, and just 59 miles at 20°F with the heater running. For example, an EV with a 240-mile range might be able to drive round-trip between Los Angeles and Palm Springs on a full battery in mild weather, but with the air conditioning engaged in a 95°F heatwave, its range would be reduced by about 40 miles and the driver would need to recharge at least once. 

 

Gasoline-powered cars lose range, too1

  • 20°F with cold start

    20°F with cold start

    -11% decrease
    in driving range
  • 20°F with warm start

    20°F with warm start

    -6% decrease 
    in driving range
  • 95°F with A/C on

    95°F with A/C on

    -17% decrease 
    in driving range
Electric vehicles aren't uniquely unsuited to extreme temperatures. Testing by the Argonne National Laborate has found that gasoline vehicles suffer range loss, too, though this phenomenon is more commonly talked about as "reduced fuel economy" or "reduced mileage." When the weather is very cold, they typically have to burn extra fuel to bring the engine up to operating temperature—this is known as a "cold start." Engine fluids are also less efficient when cold. When it's really hot, they have to burn extra gas to run the air conditioner. In fact, by percentage, gasoline vehicles suffer the same range penalty at 95°F with the air conditioning on as EVs do.
Why EV range drops in extreme weather

Reason No. 1: Batteries don't like extreme temperatures

Like any car component, the high-capacity lithium-ion batteries in an EV have a temperature range that they work best within. As temperatures fall, diffusion, conductivity, and reaction rates inside the battery cells drop. This leads to increased voltage perturbation and heat generation, consuming energy that could've otherwise propelled the vehicle. At very low temperatures, extra energy may be used to heat the battery to prevent damage.

 

Similarly, at elevated temperatures, a cooling system must run to keep the battery from overheating. This also uses extra energy and thus effectively reduces driving range. Aggressive driving results in more heat generation, increasing battery cooling demands.

Electric car battery pack

Reason No. 2: Climate control uses a lot of electricity

The two biggest decreases in EV driving range in AAA's testing came when climate control was turned on. As anyone who's ever paid a utility bill during a hot summer or cold winter knows, air conditioners and space heaters use a lot of electricity.

 

Using the heater at below-freezing temperatures produced by far the largest drop in range. Unlike gas-powered vehicles, where the engine produces heat as a byproduct of burning fuel and this can be used to heat the cabin, EVs have to run a separate electric heater. 

Climate control temperature knob
What you can do

Embrace efficiency (and savings)

The impact of the weather is more keenly felt by EVs because charging their batteries takes longer than refilling a gas tank, but they have the advantage of being much more cost-efficient because electricity is cheaper per mile than gasoline. AAA’s study found that driving an EV 1,000 miles with the A/C on when it’s 95°F outside adds about $8 more in electricity costs than driving at 75°F. By comparison, a gasoline vehicle rated at the U.S. average of 23.6 mpg would require an additional $21 in gasoline (and that's with the relatively low gas price of $2.43 per gallon).

Plan ahead

Check the forecast ahead of a long-distance trip to see if you'll be traveling in very hot or cold weather. If so, plan for more frequent stops to charge, and map out the charging stations you'll be using and the distance between them.

Pre-heat or pre-cool before unplugging

Make time to warm up or cool down the inside of the vehicle while still connected to the charger. This lets the battery save its charge for driving.

Dial the climate control back a little

There's no avoiding using the heater or air conditioning in freezing or sweltering weather, but if you're trying to stretch out your driving range, use them modestly. Just like an indoor thermostat, it's more efficient to set the climate control to a comfortable temperature and dress appropriately than to run it on blast. 

Park in a garage, if possible

Leaving the vehicle indoors can help keep the cabin temperature stable between drives, instead of letting it match the extremes of the weather outside.

Electric car icon
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Lohse-Busch, H., Duoba, M., Rask, E., Stutenberg, K. et al., "Ambient Temperature (20°F, 72°F and 95°F) Impact on Fuel and Energy Consumption for Several Conventional Vehicles, Hybrid and Plug-In Hybrid Electric Vehicles and Battery Electric Vehicle," SAE Technical Paper 2013-01-1462, 2013, https://doi.org/10.4271/2013-01-1462.

 

Information taken from "Icy Temperatures Cut Electric Vehicle Range Nearly in Half," American Automobile Association, Feb. 7, 2019, and "AAA Electric Vehicle Range Testing," American Automobile Association, February 2019.

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