Generator sizing FAQ
How does WattSizer calculate starting watts?
It adds the running watts for selected loads, then checks each appliance as the largest single starting load while the others are already running.
Should I add every starting watt together?
Usually no. Motors rarely all start at the exact same moment, but the calculator includes an all-at-once mode for conservative checks.
Can I run a generator indoors?
No. Fuel-burning generators must stay outside and away from doors, windows, garages, porches, and vents because carbon monoxide can be deadly.
Can I plug a generator into a wall outlet?
No. Home wiring needs listed transfer equipment installed by a qualified electrician.
Can this size medical-device backup power?
Only as a planning estimate. Verify your device power supply and follow manufacturer or clinician guidance.
Never operate a fuel-burning generator indoors, in a garage, on a porch, or near open windows. Use a listed transfer switch or interlock installed by a qualified electrician for home wiring, and verify actual device nameplates before buying equipment.
Medical-device backup should be reviewed with the device manufacturer, clinician, or power supplier. This calculator is only a planning estimate.