Size a whole-home or essential-load generator for your home.
Generators have two ratings and both have to be satisfied. Running watts is the steady load — add up what you genuinely want live during an outage, then add about 1,200 W per ton of air conditioning if the AC is on the list. Starting watts is the momentary surge when a motor kicks in, roughly three times its running figure, and only the largest single motor matters because they rarely start together. Size the machine to whichever is greater: the running load plus your headroom, or the surge divided by about 1.3, since generators tolerate a brief overload of that order. Deliberately choosing an essential-loads generator over a whole-home one is the usual right answer, because it is half the size, half the fuel and covers everything that actually matters.
Home Generator Size
Running = essentials + 1200 W per AC ton; surge = running + max(largest motor start, AC start at 3000 W/ton); size = max(running x (1 + headroom%), surge / 1.3)
Sizing guidance only. Standby generator installation involves fuel supply, exhaust routing and a code-compliant transfer switch, and carbon monoxide from portable generators is lethal indoors — use a licensed electrician and follow the manufacturer's siting instructions.
For a typical 2,000 sq ft home with central AC, 20-24 kW. Trimming to essential loads — fridge, freezer, lights, heating controls, well pump — usually fits in 8-12 kW.
Yes, for anything wired into the house. Backfeeding through a socket or an unswitched connection can energise the utility line and kill a lineworker, and it is illegal in most jurisdictions.