How to Size a Whole-Home Standby Generator

Whole-home standby generators are typically sized by adding up the running watts of everything you want to power simultaneously — HVAC, well pump, water heater, kitchen appliances, and general circuits — then sizing to the total plus headroom for the largest motor's starting surge (usually your AC compressor or well pump).

Many standby installations are sized to cover 'essential circuits' (not literally every outlet in the house) rather than 100% of a home's theoretical maximum draw, which keeps the unit size — and cost — more reasonable while still covering HVAC, refrigeration, and daily living needs.

A licensed electrician doing a load calculation for your specific home and panel is the reliable way to size a standby installation — general wattage guides (like ours) are a useful starting point for portable/power-station sizing, but a permanent whole-home standby installation is a bigger, code-governed decision worth professional sizing.