Power Calculator

Estimate the generator power you need for your home, workplace, construction site or business by selecting your appliances. The calculation takes into account the running power of the appliances, the highest starting load, a 20% safety margin and a power factor of 0.8.

Motor-driven equipment such as air conditioners, booster pumps, pool pumps, lifts, compressors and pumps draws its highest power at start-up, not while running; the tool accounts for this separately. For air conditioners, enter the BTU rating; the tool estimates electrical power as roughly BTU/h ÷ 11 (e.g. 12,000 BTU ≈ 1,090 W). Conventional (on-off) compressor air conditioners draw about 3 times their running power at start-up, while inverter units start softly. If you have several air conditioners of different capacities, you can duplicate the row.

For pumps, you can enter the motor power in kW and select the starting method: with direct-on-line (DOL) starting, the motor draws about 3 times its running power from the generator at start-up; with star-delta starting, about 2 times; and with a soft starter, about 1.5 times. With the right starting method, the same pump can be run from a much smaller generator. Values are based on typical equipment; if you know the power on your appliance’s rating plate, use that instead.

This tool is for preliminary sizing. Lifts, large pump sets and industrial loads call for a professional power analysis; contact us.