Sizing calculator
What size generator does your house need?
Most homes with one central AC need 20 to 26 kW for whole-home coverage with load management. Homes with two AC systems, heat-pump backup strips or all-electric appliances usually need 26 to 48 kW. Essential circuits alone run 10 to 14 kW. Use the calculator for your starting range.
Estimated sizeStarting point
This is a starting range, not a load calculation. AC starting current, your panel schedule and fuel supply decide the final size. Your estimate is attached to your quote request automatically.
How we size a generator
We add up the loads that could run at the same time, then check the single largest motor start, usually the AC compressor, against what the generator can deliver without the voltage sagging. Under NEC 702.4, a whole-home automatic system has to carry everything it can transfer, or use load management to keep large loads from running together.
Load management is why a 24 kW unit can cover a house that adds up to far more on paper: the switch holds off the AC or the range until there's capacity, and you rarely notice.
Sizing questions
What size generator do I need for my house?
Most single-AC homes of 2,000 to 3,000 square feet land at 20 to 26 kW when the AC and large appliances are load-managed. Two AC systems, a heat pump with electric backup strips, or an all-electric house push it into the 26 to 48 kW range. A load calculation from your panel and AC nameplates decides it. Our sizing calculator gives a starting range.
Will a standby generator run my central air conditioner?
Yes, if it's sized for it. Starting current is the hard part, not running load: a compressor can pull several times its running amps for a moment. A soft-start kit on the AC, load management in the transfer switch, or a larger unit solves it. We size from your AC nameplate, not a guess.
Is a bigger generator always better?
No. An oversized generator costs more up front, burns more fuel at light load, and on natural gas may need a larger meter. A right-sized unit with load management usually covers the same house for less.
What information do you need to size my generator?
A photo of your main panel with the breaker labels, the nameplate on each outdoor AC or heat pump unit, your fuel type, and a list of big loads like a well pump, pool pump, EV charger or shop equipment. That's enough for a load calculation.