The answer is more involved than you might think. The time to charge an electric vehicle (EV) can vary drastically depending on the vehicle’s hardware and the power of the charging station. You might be used to seeing this number quoted in hours from ‘empty’ to ‘full’, but that’s not the most practical way to estimate the charge time. Since most EV drivers never drive their car all the way to zero, it’s easier to look at the miles of range added for every hour plugged in.
Getting the fastest charge
You'll learn about the formula to calculate your EV’s estimated charge time here, or you can also find an EV Charger that is perfectly suited to your vehicle’s make, model, and your installation preference. When we match you to a charger, we’ll also share a summary of your vehicle’s various power stats that affect the charge time like the battery acceptance rate and size.
What are all the factors that determine charge time?
To find your EV’s charge time manually, start by finding a few figures:
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Battery size: Electric vehicles can be equipped with various battery pack sizes that determine the amount of energy stored in the vehicle (also known as an EV’s range). This number should be reported in kWh in the vehicle specs.
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Charging station output power: The amperage (A) and voltage (V) determine the maximum power that can be supplied to an EV at any given time.
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Battery acceptance rate: The maximum power an EV can accept from a charging station.
What is the battery acceptance rate?
The battery acceptance rate is the limiting factor that determines the maximum amount of power your EV can accept when charging. This means that no matter how powerful a charging station is, the speed at which you can charge will always be limited and managed by the vehicle.
For example, a 2020 Chevy Bolt has an acceptance rate of 7.2 kW. A 32A HCS-40 will add about 24 miles of range per hour of charging. A 40A HCS-50 will not charge it any quicker because it is limited by the acceptance rate. So, our recommended station would be an HCS-40 for the fastest possible charge.
If you think you might add another EV with a higher acceptance rate to your family, you can always size up to a more powerful charger. It won’t affect how quickly the Chevy Bolt charges or harm the vehicle, but a more powerful charger, for example, would charge an Audi E-Tron SUV quicker—31 miles of range per hour with the HCS-50 versus 25 miles of range with the HCS-40 because that EV has a higher power acceptance rate.
Calculating charge times
First, find the output power of the charging station by multiplying the amperage and voltage, then divide by 1000 to convert the number to kilowatts (kW) to make it more manageable.
For example, you’re looking at an HCS-60 EV Charger. The voltage is 240 and the amperage is 48.
240V x 48A = 11,520 W
11,520 W / 1000 = 11.52 kW = charging station output power
Second, find hours to a full charge by dividing your EV’s battery pack size by whichever of these limiting factors is lower: the vehicle’s acceptance rate or the charging station’s output power.
Continuing the previous example, you’re planning on using the HCS-60 to charge a Tesla Model 3 Long Range. The battery pack is 75 kilowatt hours (kWh), a total range of 310 miles, and an acceptance rate of 11.5 kW. Because the Tesla Model 3’s acceptance rate is just slightly lower than the HCS-60's output power, we’ll use that as our limiting factor.
75 kWh / 11.5 kW = 6.52 hours for a full charge
Finally, find the miles of range per hour plugged in by taking the total range of the EV, in this case 310 miles and divide by the 6.52 hours to a full charge
310 total miles / 6.52 total hours = 47.5 miles of range per hour plugged in
Remember, if you don’t feel like finding those stats to complete those equations, we can help you find your EV Charger. All you need to have ready is your vehicle make, model, and whether you’d like to hardwire or plug-in your station. We’ll provide a single recommendation to meet your needs.