Generator Size Calculator

Generators are rated twice, by the watts they hold continuously and by the watts they can supply for a moment while a motor starts, so sizing one means working out both. List the running watts of each appliance and mark which ones have a motor, and this adds the running total, applies a surge multiplier of 1x, 2x or 3x, and adds only the largest single surge, because motors start one at a time. The multipliers are rules of thumb and are named in every result; a nameplate starting wattage beats them. Nothing here covers installation: a transfer switch or interlock is a licensed electrician's job, and backfeeding a house through a wall outlet can kill the line worker restoring your power.