Miles of range per hour is a practical way to compare home chargers. Instead of talking about kilowatts, it tells you how far the car will travel after one hour of charging. This article explains how the figure is calculated and why it depends on both the charger and the vehicle.
The formula
Range added per hour equals the charger's power in kilowatts multiplied by the car's efficiency in miles per kWh.
Miles per hour = charger power (kW) x efficiency (miles per kWh)
Efficiency describes how far a car travels on each kWh of energy in its battery. It varies with the vehicle, driving speed, temperature, and terrain. For easy arithmetic, this article uses 4 miles per kWh as a round number. Your car's actual figure may be higher or lower.
Worked example
At 4 miles per kWh, a 9.6 kW charger adds about 38 miles of range per hour, before losses. An 11.5 kW charger adds about 46 miles per hour. The higher-powered unit covers more distance in the same hour, as long as the car can accept that power.
| Charger power | Range added per hour at 4 miles per kWh |
|---|---|
| 7.2 kW | about 29 miles |
| 9.6 kW | about 38 miles |
| 11.5 kW | about 46 miles |
Range per hour versus range per night
To plan an overnight charge, multiply the range per hour by the hours the car is parked. Eight hours at 38 miles per hour adds roughly 300 miles of range. A battery holds only so much energy, though, so the session ends when the battery is full, and the total added range is capped by the battery size.
Why real results differ
- Charging losses. Some energy is lost as heat during conversion, so the car gains slightly less than the simple formula predicts.
- The onboard charger. If the car accepts less power than the charger supplies, the lower number applies.
- State of charge. Charging usually slows near full, which reduces miles per hour late in a session.
- Driving conditions. Heavy, fast driving uses more kWh per mile, and cold weather can reduce efficiency.
Using the figure to compare chargers
When two chargers are compared for the same car, the difference in miles per hour follows directly from the difference in kW. A 9.6 kW charger gives 9.6 divided by 11.5 of the miles per hour that an 11.5 kW charger gives, so the faster unit is about 20 percent quicker on paper. Confirm the car's accepted AC power before assuming that gain.
How this applies to EVIQO chargers
EVIQO's product descriptions state about 38 miles of range per hour at 40 amps and about 46 miles per hour at 48 amps. These figures match the 4 miles per kWh arithmetic above. The 40-amp option is available as a 9.6 kW NEMA 14-50 plug-in unit, and the 48-amp option is available as an 11.5 kW hardwired unit. The NACS models for Tesla use the same amperage ratings. Each charger includes a 25 ft cable and a 3-year warranty.