Free tool · Size before you shop

You probably don't need the biggest generator on the shelf.

Generators are sold on fear and bought in panic, and the result is usually the wrong size in both directions. Check off what genuinely has to run in an outage, and this page adds it up and tells you which class of machine that actually is. Nothing you tap is stored or sent anywhere.

Two rules with no exceptions, before any shopping

Generators run outdoors only. Never in the house, never in the garage (even with the door open), well away from windows and doors. Carbon monoxide from generators kills people in the days around storms, quietly and fast.
Never plug a generator into a wall outlet. "Backfeeding" can electrocute utility workers on the lines and neighbors on your transformer, and it's illegal in many places. Cords run from the generator to appliances, or a licensed electrician installs a transfer switch or interlock. That's the whole menu.

What has to run?

Be honest: this is the must-run list for a multi-day outage, not the everything list. Wattages shown are planning estimates for typical models; the nameplate on your own appliance is the real number, and it's usually stamped on the back or bottom. Items marked "motor" briefly draw far more at startup than they do running, and the math below allows for the largest one.

Runtime beats size. A smaller generator that sips fuel and runs the essentials for days is usually more useful than a big one that drinks your stored gasoline in a night. Whatever the class, plan the fuel: stabilized gasoline stored safely outside living space, or propane, which stores indefinitely. And test-run the machine before the season, not the night the forecast changes.

Wattage figures on this page are planning estimates for typical residential models, compiled for this tool and rounded conservatively; they are not measurements of your equipment. The U.S. Department of Energy's guidance on estimating appliance energy use is the method behind the "check the nameplate" advice: the nameplate wattage is the maximum power the appliance draws. Motor-start allowances are a planning rule of thumb, not an electrical specification. For anything installed or wired (transfer switches, interlocks, standby units, well pumps), a licensed electrician is the source of truth. Estimates logged in VERIFY.md (V22, V23); safety rules V4, V27. This page is educational only and is not electrical, safety, or purchasing advice.

Where this fits: backup power is one line of eleven on your readiness score. The 3-minute readiness check tells you whether it's even your biggest gap (water and paperwork usually outrank it), and the honest sizing guide covers the fuel, noise, and transfer-switch decisions in plain English.