Tool

Charge rate calculator

Generators are rated optimistically and EV charging is a continuous load. This derates for both, then tells you what to actually set in the car.

240V is the whole ballgame. A generator with only 120V outlets caps at roughly 5 miles of range per hour regardless of its wattage — a 12,000W unit charges no faster than a 2,000W one. Set the voltage below honestly.

Generator output voltage Generator running watts (gasoline) Fuel you're running Vehicle efficiency (mi/kWh) Altitude above 3,000 ft?

Set car to–

To battery–

Range per hour–

Generator load–

How the math works

Generators are rated for intermittent household loads, not a steady draw for hours. EV charging is about as continuous as a load gets, so the calculator targets 80% of running watts — the same continuous-load derate the electrical code applies to circuits.

From there it rounds down to an amperage the car will actually offer, subtracts roughly 10% for onboard charger and cable losses, and converts to range using the efficiency you picked. Cold weather is where most published estimates fall apart, so it's a first-class input here rather than a footnote.

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