What Size Generator to Charge an EV?
A 2,200W inverter handles level 1 EV charging: the standard 120V cord draws about 1,400 watts steadily and adds 4 to 5 miles of range per hour, roughly 40 overnight. Level 2 at 9,600W demands a 12,000W portable and, honestly, a reason; the arithmetic below says the gas is better spent almost anywhere else.
Wattage by type
| EV charger type | Running | Starting |
|---|---|---|
| Level 1, 120V 12A (planning number) | 1,400 W | no surge |
| Level 1 dialed to 8A | 950 W | no surge |
| Level 2, 16A 240V | 3,800 W | no surge |
| Level 2, 32A 240V | 7,700 W | no surge |
| Level 2, 40A 240V | 9,600 W | no surge |
What it takes with company
Same engine as the wattage picker: running total plus the single biggest start spike, then the smallest class that carries it with 20% headroom.
| Load list | Running | Peak | Buy |
|---|---|---|---|
| Level 1 charging alone | 1,400 W | 1,400 W | 2,200W inverter |
| Level 1 + fridge + the basics | 2,300 W | 3,800 W | 3,500W portable |
| Level 2 at 16A + the basics | 4,000 W | 4,000 W | 5,000W portable |
The details that change the answer
The arithmetic deserves daylight. A portable generator delivers about 5.5 kWh per gallon of gasoline; an efficient EV goes about 3.5 miles per kWh; so generator-charging buys roughly 19 miles per gallon, in a car you bought partly to skip gas stations. As emergency mobility (enough charge to reach a working DC fast charger) it's a fine trick. As a routine, a 19 mpg gas car with extra steps.
Mechanically it works better than EV forums feared. Charging is a steady resistive-looking load, no surge, and the car's onboard charger tolerates inverter-generator power without fuss; many EVs do object to open-frame units with no neutral-ground bond, throwing a charging fault until a bonding plug fixes the pigtail. Level 1 coexists happily with the storm basics on a 5,000W portable. Level 2 wants 240V, which means open-frame units from 12,000W (or 3,800W at a dialed-down 16 amps on a 5,000W class with an L14-30), and at that point the generator is charging the car and doing nothing else.
Worth knowing the reverse direction exists: several current EVs offer V2L (vehicle-to-load), 1,500 to 9,600W of outlet power from the traction battery. During most outages the car should probably be powering the fridge, not the generator powering the car.
Questions people ask
How fast does a generator charge an EV?
Level 1 at 1,400W adds 4 to 5 miles of range per hour after charging losses, so an overnight 10-hour run is about 40 miles for roughly 3 gallons of gas. A 12,000W portable doing level 2 at 9,600W adds about 25 miles per hour and drinks a gallon-plus per hour doing it. Enough to escape an outage zone; not a lifestyle.
Why won’t my EV charge from the generator?
Almost always the neutral-ground bond. The car’s charge cord tests the outlet for a grounded neutral, and floating-neutral generators (most inverters) fail that test, so the cord refuses. A neutral-bonding plug in the generator’s spare outlet satisfies the check. If the cord still faults, dial its amperage down; voltage sag at the plug trips the same protection.