Use this free generator wattage calculator to size the right generator for your home. Select your appliances, and we’ll add up the running watts and the higher starting (surge) watts so you can pick a generator that won’t overload.
| Add | Appliance | Running W | Starting W |
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Tip: add ~20% headroom for safety. Starting watts matter most for motors (fridge, AC, well pump, power tools).
How to use this generator wattage calculator
Tick every appliance you want to run during an outage. The tool sums the running watts (continuous draw) and calculates the peak starting watts — the brief surge when motor-driven appliances kick on. Always size your generator to the starting figure plus ~20% headroom.
Running watts vs. starting watts
Resistive loads (lights, heaters, chargers) draw the same watts continuously. Motor loads (fridge, AC, pumps, power tools) need 2–3× their running watts for a split second at startup. A generator that only covers running watts will stall when a motor surges — which is why this calculator tracks both.
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