What Size Generator for a Window AC?
A 3,400W inverter runs a 10,000 BTU window AC (1,200 running watts, 2,400 at start). A little 5,000 BTU unit runs on a 2,200W inverter; a 14,000 BTU monster wants the 3,500W class before you add the fridge. Ranges below.
Wattage by type
| Window air conditioner type | Running | Starting |
|---|---|---|
| 5,000 BTU | 550 W | 1,100 W |
| 8,000 BTU | 900 W | 1,800 W |
| 10,000 BTU (planning number) | 1,200 W | 2,400 W |
| 12,000 BTU | 1,400 W | 2,800 W |
| 14,000 BTU | 1,700 W | 3,400 W |
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 |
|---|---|---|---|
| 10k window AC alone | 1,200 W | 2,400 W | 3,400W inverter |
| AC + fridge | 1,900 W | 3,400 W | 3,400W inverter |
| AC + fridge + the basics | 2,100 W | 3,600 W | 3,500W portable |
| Two 8k units + fridge + basics | 2,700 W | 4,200 W | 3,500W portable |
The details that change the answer
A window unit is the honest way to have cooling in an outage: central AC needs standby-class power, but one cold bedroom needs a suitcase inverter. The compressor start is the usual doubling, so the sizing rule is the running watts of the AC plus the fridge, plus whichever of the two has the bigger start spike, and the combo table shows that a 10k unit plus the storm basics lands on a 5,000W portable.
Newer units change the math. Inverter-compressor window ACs (the U-shaped ones, mostly) ramp up instead of slamming, so their start figure is barely above running, and an 8,000 BTU inverter unit plus a fridge fits on a 2,200W generator that would trip on the old-style equivalent. If you're buying the AC and the generator together for hurricane season, buy the inverter AC and downsize the generator one class; the pair costs about the same and runs quieter.
Questions people ask
Will a 2,000W generator run a window air conditioner?
A 5,000 BTU unit, yes, with about half the capacity left over. An 8,000 BTU unit fits by the chart (1,800W start against a 2,200W peak) with nothing else starting at the same time. At 10,000 BTU the 2,400W start exceeds the class; move to a 3,400W inverter, or buy an inverter-compressor AC, which starts soft enough to stay on the small generator.
Window AC or portable AC on a generator?
Window, and it is not close. A dual-hose portable AC of the same nameplate BTU delivers noticeably less cooling per watt (single-hose is worse still), so on generator power you pay the same watts for less cold. If the window really cannot take a unit, a portable works; size it one line up in the table.