How much electricity does an electric car use?


Rather than give you the ‘boring’ answer, which you can look up for any electric car in existence, I’m going to try to convey a sense of the POWER used by an electric car when charging and driving. In case you came here looking for that, here’s a link to a Wikipedia article with the details of energy consumption for many electric cars.

Let’s look at car charging. Consider a Level 2 home car charger. (Wikipedia article on car chargers.) These are the type that wire into your home’s breaker box using a 240V line (in the USA). These charge your car at up to ~7.2 kilo-Watts (7,200 Watts), drawing ~32-40 Amperes of current.
(note: for the rest of the article, I’ll use the shorthand notation – ‘V’ for Volts; ‘W’ for Watts; ‘kW’ for kilo-Watts, and ‘A’ for Amperes.)

This sounds like a lot, but how does it compare to other things in your house?

For comparison, a typical bright, old, inefficient incandescent light bulb draws 100W, so the charger is about equivalent to 72 of these light bulbs – probably more than you have in the entire house! What about other appliances?

Hair dryers and microwave ovens use ~1500W. That’s also almost the maximum power than can be delivered through a normal US 120V outlet. Charging the car at home is like running 5 hair dryers. How long depends on how much juice your car needs, which depends on the size of the car’s battery and how depleted it is. So while the car is charging at home, it’s like running 5 hair dryers continuously for the time it’s charging.

Home car charger is about the same as 5 hair dryers

Another appliance that makes a good comparison is your home’s central air conditioner. A typical, mid-sized (4-ton or 48,000 BTUs/hr) air conditioner uses ~4,000W, so charging the car is like running a bit less than two central AC systems. A water heater is usually 4,500W-5,500W, so the car is pulling more than the water heater too!

This should give you a bit of an idea of just how much power you’re using to charge the electric car. It also gives you an appreciation for the amount of energy those batteries hold. But, as they say, “you ain’t seen nothing yet!”

How much energy does an electric car use while driving?

I drive a Chevy Volt. This is an electric vehicle (EV) that has a gas engine to charge the batteries as necessary. But I use it almost exclusively as an EV. In fact, since purchasing it this Spring, I’ve used less than 1/2 gallon of gas! Here’s a link to an article I wrote on why I bought a Chevy Volt

The Chevy Volt is a very efficient EV, but it’s still in the ballpark of other EVs like the Tesla Model 3, Chevy Bolt, Volkswagen eGolf, etc. so the following comparisons will give you a pretty good idea of the power used for most EVs.

While I was driving home today, I glanced at the consumption gauge. This tells me how many kilo-Watts (kW) the electric motors are using at any given moment. Here’s some numbers for comparison:

  • Driving at 30mph: 5-8kW
  • While driving at 40mph: 10kW
  • While driving at 60mph: 14kW
  • While accelerating from a stop: 50kW+

And of course hills make a huge difference! These numbers give you a general idea of how much power it takes to drive.

Refer back to the discussion about charging. 7.2kW sounded like a lot of power. But it takes more than that to push the car around at about 40mph! Maybe 7 hair dryers or 2-3 central air conditioners just to slowly cruise around town. And accelerating – 50kW or more! That’s a phenomenal amount of power. About 12 AC systems, or 35 hair dryers! Good thing you only accelerate for short amounts of time or that battery would be toast, quickly!

How Powerful are Public Car Charging Stations?

A home car charger is extremely convenient – no more gas stations! But, even as powerful as they are, it still takes several hours or more to top off your car. That wouldn’t be very useful if you were taking a road trip. Fortunately, Tesla and others have created a network of high power “DC” fast chargers.

A DC (direct current) fast charger pumps energy straight into your car’s batteries at an extremely high current. Keep in mind that there are multiple standards and not all cars support DC fast charging (my Chevy Volt doesn’t).

How much power? On the low end, they run about 40kW. Old Tesla Superchargers go up to 120kW and their new one, Version 3, can put out an astonishing 250kW. Future standards include specs for up to 350kW and even more. Using our previous comparisons, 120kW is 80 hair dryers. 250kW is 167! And, if you’re thinking you might want one for your home, FORGET IT! 250kW is more than 1000 Amps. A typical good home service panel, and the line that runs from the utility pole to the house, is usually only capable of carrying 200 Amps.

Why do they need so much power? If you’re taking a road trip, you want to juice up as fast as possible. People are used to spending 5-10 minutes at a gas pump, so anything more than that gives the perception that it’s taking too long.

If you’ve got a 60kWh car battery, you might use 50kWh (maybe 200 miles) on a long trip before you stop to power up and grab a snack. With a 40kW charger, adding 50kWh takes well over an hour, which would annoy most people. At a 250kW Supercharger, you’re more in the range of a typical gas fill.

Note: the calculation isn’t simply dividing the battery capacity by the charging power because the charger modulates the charging to avoid overheating the batteries which shortens their life. So most charging systems charge quickly up to some level, maybe 75%, then slow down considerably. But 250 kW will extend the range of your Tesla fast enough! By the time you’re back from your ‘nature break’, the battery will be charged enough to get you to your next stop.

What does it cost to drive an electric car?

Modern electric cars usually have batteries with a capacity of 24 to 100 kWh – kilo-Watt-hours. That’s a measurement of the energy stored in the batteries. One kWh means one thousand watts for one hour. So a 24 kWh battery holds enough energy to supply 24,000 Watts for one hour. For comparison, a typical house consumes from 20kWh to 100kWh for one full day. At a cost of $0.15 per kWh, that means for every 10kWh of energy, you’re paying $1.50. Filling an empty 50kWh battery at home costs ~5*$1.50 = $7.50.

How far does that get you? Most electric cars get between 3 and 5 miles per kWh consumed. Let’s use 4 miles per kWh as a typical number. That’s 4 miles for 1 kWh which costs $0.15. That means the EV could drive 40 miles for $1.50. Not bad!

In fact, for my Chevy Volt (and the eGolf which I had before), which I use for all my local driving (about a 35 mile radius from my home), I typically get between 5 and 6 miles per kWh because the average speed for local drives is lower so the car isn’t fighting the wind as much. So for me, I can drive 50-60 miles for that $1.50. Compared to gas, which costs $2.25-$3.00/gallon these days, that’s a bargain, even if you drive a very efficient gas powered car.

Hopefully, you now have an intuitive feel for the amount of power “under the hood” of an electric car. These examples are intended to give you an appreciation for the batteries and drive train, and maybe help you understand why electric cars have been relatively slow to develop. Packing that much energy into a battery is truly amazing, but there’s still a long way to go. A thousand pounds is a lot of batteries, but as batteries get more storage capacity and weigh less, we’re going to see even more efficient long-range electric vehicles.

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