How many watts does a window air conditioner use
While running, a window air conditioner draws from 900 up to 1,200 W. Starting it needs 1,800 up to 2,400 W for that first second. A 2,000 W portable is the smallest one that can run it.
Watts for running and starting
| Load | Running | Starting |
|---|---|---|
| Window AC, 10,000 BTU | 900 to 1,200 W | 1,800 to 2,400 W |
Source: Champion's wattage chart, 04-17-26. Find the exact figure for your window air conditioner on its nameplate, listed in watts or in amps. Amps times 120 V gives the watts. Use 240 V only when the load runs on a two-pole breaker, for instance a well pump.
The smallest generator that can start one
A generator must carry 1,200 W, which is at most 80% of its rating. It must also give 2,400 W at startup. For both jobs, the smallest common portable size is 2,000 W, with power left over. Other loads add their running watts to that same generator.
AC, 10,000 BTU window unit with other loads
| Window AC, 10,000 BTU plus | Running | Peak at a start | Smallest portable |
|---|---|---|---|
| lights, TV and the router | 1,770 W | 2,970 W | 3,000 W |
| a freezer and lights | 1,850 W | 3,050 W | 3,000 W |
| a 1/2 hp sump pump and lights | 2,400 W | 3,600 W | 3,000 W |
| a microwave | 2,400 W | 3,600 W | 3,000 W |
| a 1 hp well pump | 3,200 W | 5,200 W | 5,000 W |
Running watts add up, and just the biggest motor start adds to the total. For a portable, starting output sits about 25% above the running rating. The appliance wattage chart lists every load.