Dear Car Talk:
A question about electric vehicles! How is an EV cooled and heated?
I assume an electric motor runs the compressor for cooling. And I assume heating is done by either a heat pump or with resistance heating.
My question is, since electricity is used for both of these things, how does this affect the range? — Jim
Good question, Jim.
The answer is complicated. There are different systems, and lots of variables. Unless you count “water bottle” and “electric socks,” you’re right that there are two types of heaters used in EVs. There are resistance heaters (basically, a toaster), and heat pumps, which pull heat out of the air — even cold air. A heat pump is far more efficient.
To get a sense of how they affect range, we called our pal Tom Voelk, who tests lots of EVs for his “Driven” car review series on YouTube.
Tom says that in his experience, the effect on range varies, depending on the actual outside temperature, the size of the cabin, and how toasty you want your cheeks to be. But for old style, toaster/resistance heaters, Tom says range can drop by a third or even more in sub-freezing weather. For EVs with heat pumps, he’s seen range drop by around 15% under similar conditions. Quite a bit less.
Of course, all that loss in range is not just due to using the heater. The loss is greater when using heat because it’s, what? Cold out! And batteries are already less efficient in cold weather.
When you’re using air conditioning, it’s usually hot out. Unless you’re a weirdo. So, the batteries are already working much more efficiently. Tom says that with constant air conditioning, he typically sees about a 10% drop in range. You can reduce those losses if you use what’s called pre-conditioning.
A number of EVs now allow you to pre-condition the cabin before you drive away. So, you can tell the car you’re leaving for a recreational root canal at 8 a.m., and the car will either heat or cool the cabin while it’s still plugged into your home charger — before you drive off and use up any range.
You can also reduce your heating demand by using a seat heater and heated steering wheel, which keep your most sensitive parts warm without having to turn the whole cabin into a blast furnace.
I hope that gives you a ballpark idea, Jim. And I sincerely hope I haven’t done Tom Voelk’s career any lasting damage today by associating him with Car Talk.
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