What size generator do I need?
Pick your home, tap what has to stay on, and watch the house light up. Same method installers use — running watts, plus the biggest motor's start surge, plus headroom.
- 24 household loads with real running and starting watts
- 10 states with outage history and local labor rates
- 0 sign-ups. Your picks stay in your browser.
Your home
Pick the closest match. It sets sensible defaults you can change in step 2.
What has to stay on?
Only what you'd actually run at the same time during an outage. Motors — A/C, pumps — are the expensive ones.
Kitchen
HVAC
Water
Laundry
General
Medical
Where you live
Sets local labor rates for the cost estimate and shows how often your grid actually goes down.
How sizing actually works
Standby generators are rated in kilowatts of continuous output. Two things set the size you need: the total running watts of everything on at once, and the starting watts of the single largest motor — compressors and pumps draw two to three times their running load for a fraction of a second on startup. Add the surge of the largest motor to the running total, then leave 20–25% headroom so the unit isn't working at its limit.
The number that dominates almost every home is central air conditioning. A 3-ton unit alone can push you from a 14 kW to a 22 kW generator. If you can accept no A/C during outages — or run only one zone through a load-management switch — the savings are significant. Read the full sizing guide →