How many watts does a Window AC (12,000 BTU) use?

About 1100 watts while running, with a start-up surge of roughly 3000 watts. Actual draw varies by model — check the nameplate on your unit.

What size generator do I need to run a Window AC (12,000 BTU)?

Plan on at least 1400 running watts with 3000 watts of surge capacity, which includes 25% headroom.

Calculator › Wattage chart › Window AC (12,000 BTU)

What size generator to run a Window AC (12,000 BTU)?

Typical draw: 1100W running / 3000W starting. Large room unit; needs a mid-size generator on its own.

SIZING PLATE1 LOADS · +25% HEADROOM

Total running watts

1,100 W

Peak (largest start)

3,000 W

Buy at least

1,400 W rated

Look for ~1,400W running / 3,000W surge or better.

Right size: Mid-size inverter (3,500W / 4,000W surge)

Typical price $600-1,400 · e.g. Champion 4250 open-frame inverter, Westinghouse iGen4500, Generac GP3500iO

RV 13,500 BTU AC (especially with soft-start), fridge + window AC, storm essentials for smaller homes. The sweet spot of quiet, portability, and real capacity for most first-time buyers.

See current prices on Amazon

One size up: Mid-size portable (6,500W / 8,100W surge)

Typical price $700-1,200 · e.g. Westinghouse WGen6500, Champion 6250, Generac GP6500

Storm essentials with margin: fridge, freezer, sump pump, furnace fan, well pump (240V models), lights and electronics together. Louder open-frame design; electronics prefer models with THD under 5% or an inverter.

See current prices on Amazon

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Real outages aren't one appliance. Adjust the full load below — your Window AC (12,000 BTU) is pre-checked.

This site earns commissions from qualifying purchases made through links to Amazon and other retailers, at no extra cost to you. Wattage figures are typical estimates — actual draw varies by model. Always verify against your appliance's nameplate, and consult a licensed electrician for any panel or hardwired connections.