An EV’s power output is measured in kilowatts, and a 100-kW output roughly equates to 134 horsepower. Unlike a gasoline vehicle’s maximum power output, which is not an exact science, an electric vehicle’s power output is accurate, as it directly reflects the electrical energy being used.
To determine how much power will flow to your car’s battery, multiply the volts by the amps and divide by 1,000. For example, a 240-volt, Level 2 charging station with a 30-amp rating will supply 7.2 kilowatts per hour. After one hour of charging, your EV will have an added 7.2 kilowatt hours (kWh) of energy.
Let’s say you have an electric motor rated at 200 kilowatts (kW) at peak power output. If you ran that motor for 30 minutes you would use 100 kWh of energy — 200 multiplied by 0.5 (of an hour) equals 100 kWh. If how far your electric car can travel on one charge is important to you, as a general rule of thumb, you want an EV with a big battery.
A battery’s capacity is commonly rated at 1C, indicating that a fully charged battery rated at 1Ah should provide 1A of current for one hour. By adjusting the discharge rate, the battery can provide different levels of current over varying durations.
The maximum amount of electrical current that can be delivered to your vehicle’s battery is the amp rating. Volts and amps deliver kilowatts (kW) of power to your EV’s battery, which means the kilowatt value listed in the charging station specifications is the rate at which your vehicle will charge.
All electric car batteries have a usable capacity that's slightly less than the gross capacity because this helps extend the life of the battery pack. That buffer prevents it from ever being completely charged. For example, the Audi Q8 e-tron's battery pack has a gross capacity of 114 kWh, but its usable capacity is 106 kWh.