What size generator to run a central air conditioner?
Central air conditioner (3 ton) draws about 3,500W while running and surges to 10,500W on startup. Allowing 20% headroom, size for at least 12,600W of starting capacity.
The startup surge is what forces most people to a 10,000W+ generator. A soft-start kit cuts it substantially and is far cheaper than a bigger generator.
The surge is the number that matters. A generator rated to 3,500W will stall the moment the motor kicks in, because for a fraction of a second it needs 10,500W. Manufacturers advertise running watts, which is why people routinely buy one size too small.
Units that cover it
- DuroMax XP13000EH
13,000W starting · 24% headroom · $1,299
Sized close to your load with a little room to spare, has a CO shutoff sensor, runs on propane as well as gasoline.
Check price - DuroMax XP13000HXT
13,000W starting · 24% headroom · $1,499
Sized close to your load with a little room to spare, has a CO shutoff sensor, runs on propane as well as gasoline.
Check price - Pulsar PG15000TRCO
15,000W starting · 43% headroom · $1,499
Comfortable headroom without overpaying for capacity, has a CO shutoff sensor, runs on propane as well as gasoline.
Check price
Running more than one thing
Most people are not powering one appliance. Add everything you need at once and the calculator works out the real peak — your total running load plus the single largest surge, not the sum of every surge.
Size the whole load