Backup generator decision guides

Start with the outage data, not the sales pitch. EIA's 2024 reliability figures show the average customer losing about 663 minutes of power across roughly 1.5 non-momentary interruptions when major events are included, versus about 132 minutes when they're excluded. Translation: for most people the generator is insurance against a handful of bad storm days, not everyday inconvenience. If your state is one of the hard-hit ones, that calculus changes fast.

Then do the load math. The formula is simple: total running watts + the highest single starting wattage. If you're running 3,000 watts of stuff and your biggest motor needs a 1,500-watt surge, you need at least 4,500 watts. Aim to stay at or below about 90 percent of the generator's rated capacity so it isn't running flat out.

For reference points, Bob Vila's sizing chart puts 7,500 watts at a one-bedroom home's basics, 10,000 watts at two bedrooms including a water heater, 18,000 watts at a five-bedroom with office and garage, and 25,000 watts at full coverage of a larger home. Common running loads: fridge 600–800 W, sump pump 1,500 W, water heater 3,000–4,500 W, electric furnace 5,000–25,000 W.

There is a legitimate case for buying no generator at all. If outages are short and you have no well, no sump pump and no medical equipment, a battery power station and a good plan for the fridge may cover you for a fraction of a $5,090 install.

How to choose

Write down what must stay on

Well pump, sump pump, furnace blower, fridge, medical devices, internet. Everything else is negotiable, and negotiating it is how you avoid a 26 kW quote.

Add starting watts only once

You add the largest single surge, not every appliance's surge. Salespeople who add them all end up quoting you a much bigger unit.

Leave headroom, but not much

Running at no more than about 90 percent of rated capacity prevents overheating and nuisance shutdowns. Two size classes of headroom is just money.

Check whether your well or sump is the real driver

No power means no water on a well and a flooding basement on a sump. Those two loads justify backup power more often than air conditioning does.

Look up your own state's outage record

National averages hide enormous variation between states. Your utility's reliability history is the number that should drive the decision.