Start from Honda’s published figures, not from the size of the room. Honda’s Home Applications table (retrieved 2026-11-11) lists a 10,000 BTU window air conditioner at 1,500 W running and 2,200 W starting. A generator that can cover those watts, with margin, will run that unit alone. If you also want the refrigerator and some lights, add them with the largest-starting-increment method. This is not a sizing number for central air or for a mini-split; those have their own nameplates.
| Load | Running W | Starting W |
|---|---|---|
| Window air conditioner, 10,000 BTU (Honda) | 1,500 | 2,200 |
| Refrigerator or freezer, Energy Star (Honda, high running) | 192 | 1,200 |
| Those two, simultaneous running | 1,692 | — |
| Plus largest starting increment (fridge, 1,008 W) | — | 2,700 |
| Same two plus a 1/3 hp furnace fan (700 W run, 1,400 W start) | 2,392 | 3,400 |
The refrigerator’s starting increment (1,008 W) is larger than the window unit’s (700 W) in this table, so the fridge sets the surge when both are in the list. Put the window unit in the calculator as the Honda item it is, and never substitute these watts for an outdoor central-air nameplate.
This is not a permit calculation, a utility approval, or a substitute for a licensed electrician, HVAC contractor, or the authority having jurisdiction. Panel Headroom is an independent educational site. It is not a utility, a certification body, or a contractor. Electrical and generator work that is done incorrectly can cause fire, shock, or carbon monoxide poisoning. Use the adopted electrical code and manufacturer instructions; pull permits where required.