Question: How Do Electric Cars (Volt, Leaf) Heat Passengers?

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2011 Chevrolet Volt

2011 Chevrolet Volt

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Another in our irregular series of answering questions from readers, this one from John Q of Eugene, Oregon:

Question: I was wondering how an electric car provides heat and defrosting. Using batteries to generate the heat will drain them pretty fast. Maybe with the 2011 Chevrolet Volt, the internal combustion engine is run for heat? But what about the battery-only 2011 Nissan Leaf?

Answer: In brief, cabin warmth on cold days is provided via resistance heating, which--as you note--uses a lot of current.

However, theĀ  Chevy Volt offers heated driver and front passenger seats.And the Cold Climate package offered for the Nissan Leaf includes not only heated front seats but a heated steering wheel as well.

2011 Nissan Leaf

2011 Nissan Leaf

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Those items turn out to make occupants FEEL warm enough that the cabin heat may not be necessary, or can be used at lower temperatures. But simply heating seat surfaces and a steering wheel requires much less current than heating volumes of air and blowing them around the cabin.

Under some circumstances, especially if the battery pack has been cold-soaking, the Volt may switch on its engine when started until the pack has warmed up enough to be in the appropriate operating temperature range. Then it will switch off again until the pack is depleted--which is essentially how today's hybrids work.

The Leaf, of course, does not have that option. But when either car is plugged in to recharge, some energy may be diverted to keep the pack at its ideal operating range--either cooling via fans (Leaf) or liquid cooling (Volt), or heating via elements inside the pack.

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Comments (10)
  1. I was looking around for an answer to the second part of this question, i.e. range and outside temperature. I didn't really find it.
    Nissan shows a range of 62 miles in stop and go traffic at 15 F outside. Not too bad really. Unfortunately, they don't have a comparable range listed for 68 F temperature and stop and go.
    The general information on the web indicates that while heating is significant, range reduction due to heating is perhaps about 15%. Anyone else have any better data?

  2. Not every body lives in southern California. In western New York we have real winters and heated air for the defroster is a necessity, NOT AN OPTION. Heated seats and steering wheels are nice but they don't do much when the ambient temperature is 10 degrees F. and it's snowing. Where do they do their "cold weather" testing for these vehicles?

  3. @Don: Good point, and I realize I wasn't clear. Both cars also have standard-issue defrosters that blow hot air over the insides of the windshield and vent some of it back to the front side windows. Not to worry; I'm quite confident both of the cars were tested in VERY cold climates (e.g. above the Arctic Circle), as are all global new cars these days.

  4. They can get heat from the motors and controllers. Electric heat might reduce the range a bit or they could use heat pumps.

  5. The Leaf uses an Inverter type compressor for the AC system and a Resistive heater for heating the cabin. Thus, heating takes far far more energy than cooling/dehumidifying the cabin!
    Heater can take over 4,000 watts.
    AC takes less than 2,000w.
    Does the volt us a Heatpump to heat the cabin or a resistive heater like the Leaf?

  6. What is the top speed when on the generator and what is the projected EPA miles per gal when on the generator.

  7. @Don Naples: I believe Chevrolet has limited to the top speed to something like 90 or 95 mph. And the EPA has rated the Volt's combined gas mileage with the engine on at 37 miles per gallon.

  8. im live in Winnipeg so it gets down to -40oC, most cars have block heaters that you plug in so your car wont freeze up and not start, and from experience i think you would only need heated seats, defrosting windows and a much better feet warming system, cause to be fair when its that cold out i have gloves and a coat on anyway, its just my feet freeze quickly and giant boots aren't convenient. Also, Wouldn't solar powered AC be ideal cause if its hot outside its more than likely going to be Sunny.

  9. I see comment that an electric heater can consume twice the energy required for cooling.
    Why not consider a reverse-cycle aircon system, much like you may have in your home?.
    A retrofit such as this would also eliminate the need for any engine coolant fluid leak complications in the cabin of your car.
    Another earlier comment I see, was about Heat Pumps.
    These (Peltier Effect) devices consume significant amperage, and in my view are the least efficient electric means for heating the cabin.

  10. Which electric cars have a pre-warmer for car? Ie: When plugged in at home, you can set the pre-warming of car say, 1 hour prior to departing using electricity from grid (as opposed to from battery).

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