Generator Wattage Calculator

Add appliances (with surge), choose method, set headroom, and see totals for 120V and 240V. Save & load your list.
Values are typical; always check your nameplate or manual.
Starting watts are higher for motors/pumps/AC compressors. Resistive loads (heaters, kettles) usually have starting ≈ running. Assign each item to 120V or 240V according to its supply.
Surge method
ItemQtyVoltageRun (W)Start (W)
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120 V Circuit
240 V Circuit
Rule of thumb: generator size ≥ Total running watts + surge allowance. For split-phase generators, ensure each 120 V leg and the 240 V loads are within ratings and reasonably balanced.
All wattages are approximate. Always verify against the device nameplate/manual and consider professional advice for critical loads.

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