The biggest difference between internal combustion vehicles and electric vehicles (EVs) is the fuel: instead of putting gas or diesel in your tank, you charge up your battery using electrical energy. Thinking in terms of kilowatts, kilowatt-hours, and amps isn’t yet that intuitive for people who are used to dealing in gallons of fuel, but it’s helpful to understand these concepts as you dive into the world of EVs.

In this article, we'll explain all the units involved and see how they can be used to calculate useful results like how much it will cost to drive a certain number of miles in your EV.

An EV's battery capacity is measured in kilowatt-hours

For internal combustion vehicles, you measure fuel with gallons: you know how many gallons your fuel tank can fit, how far you can go on a gallon of gas, and how much a gallon costs at the pump. Instead of liquid fuel, EVs use electrical energy, which is measured in kilowatt-hours, or kWh for short.

Let’s use a Ford E-Transit van as an example: its battery holds 65 kWh and it has an estimated range of 126 miles.

You can think of the kWh of the battery as the size of the fuel tank: that’s how much energy your vehicle can store. We can use these two numbers – battery capacity and range – to estimate how much energy the vehicle will consume per mile.

How much energy will my vehicle use per mile?

To estimate how many kWh an EV will use per mile, you can use the following formula:

Given the range and battery size above, we can calculate that, on average, a Ford E-Transit will use:

65 kWh / 126 miles = 0.51 kWh per mile

You can think of that as similar to the miles per gallon (mpg) rating of a car, but a little different: the fewer kWh are needed per mile, the more efficient the vehicle. For most passenger cars, you can look up this information on fueleconomy.gov.

It's important to keep in mind that the vehicle's energy efficiency can be affected by many factors such as temperature, load, and driving style – just like mpg in a gas or diesel car.

Using the vehicle's efficiency, you can estimate how much energy it will use to drive a certain distance, and how much that will cost in terms of electricity. For example, if you drive 50 miles in a Ford E-Transit, we can estimate that will use about:

50 miles * 0.51 kWh / mile = 25.5 kWh

If your electricity price is $0.22/kWh (the average commercial price in CA according to the EIA), then charging the vehicle up to drive 50 miles will cost about:

25.5 kWh * $0.22 / kWh = $5.61

That’s 60% less than the fuel cost for a gas version at 15mpg, which would have been about $15!

So why is it called a kilowatt-hour? That’s because it’s how much energy you would get from a 1 kilowatt charger in 1 hour. This allows us to estimate how long it would take us to charge this van. Let’s dive into kilowatts and how they work.

How long will it take to charge?

When you’re driving an internal combustion vehicle, you don’t really have to worry about how long it will take to fuel up. With electric vehicles the charging time is a bit longer, and it depends on the power being delivered by the charger.

The unit for charger power is the kilowatt, or kW.

The time it takes to charge your vehicle will depend on how many kWh your vehicle needs and the power provided by the charger. If you drove 50 miles and used 25.5 kWh, then to estimate how long you’ll need to charge you can divide the 25.5 kWh by the power of the charger:

One thing to note is that in reality the charging power is not constant - it depends on the battery’s temperature, condition, charge level, and vehicle's maximum charging speed. Check out this article from EVgo for more details.

When installing a charger for your EV at home or at your facility, in addition to selecting the power level in kW you'll need to make sure your electrical panel and utility connection can supply enough current for the charger and all of your other equipment. Also, always make sure to work with a qualified electrician to make sure everything is done correctly.

Conclusion

While kilowatt-hours, kilowatts, and amps are different from gallons of gas or diesel, there are a lot of similar concepts. Once you’re equipped with the knowledge of how to convert between them, you can start to assess the capabilities and cost of an electric vehicle!

If you’re evaluating EVs for your fleet, and are trying to understand the options available, how to charge, and how much everything will cost, our team at Flipturn is here to help. Get in touch with us at hello@getflipturn.com!