What size generator do you actually need?
Set up your appliances once in the House calculator and every sizing tool on this site — including this one — uses it. Get a running and peak wattage total and see which generators can actually cover the load, no signup, no email gate.
Your appliances
11 of 11 House appliances count toward the numbers below.
Generators have the most headroom, so all three tiers count by default — narrow it to see what a smaller unit would still cover.
Your wattage
- Running
- 5,980 W
- Peak (surge)
- 8,380 W
Peak load assumes Window AC (10,000 BTU) is the motor starting under load — the largest surge among your selections.
Shop for: at least 7,500 W running — that keeps your load at ~80% of rated output, the margin installers size to. Running a generator flat-out sags voltage and shortens its life.
Generators that fit
Prices are typical street prices as of July 2026 — check the current listing before buying.
- ★ Best overall for home backupWestinghouse WGen9500~$1,1009,500 W run · 12,500 W start · Open frame · Gasoline74 dBA · up to ~12 h at 25% load
Our top picks, if you'd rather skip the math
Three picks that cover most buyers — each argued honestly, counter-cases included, on the full recommendations page.
How this calculator works
Every appliance in the picker carries two numbers from published sizing charts and manufacturer datasheets: its running watts (continuous draw) and its starting watts(the 2–3 second surge motors pull when they kick on). We total the running watts of everything you select, then add the single largest surge on top — not every surge at once, because motors don't all start in the same instant. That's the same method an installer uses on a clipboard.
Generator matches come from manufacturer-published ratings, and we flag any match where your load would sit above 80% of the unit's rating — a generator run flat-out sags voltage, drinks fuel, and wears early. Your appliance nameplates are the ground truth; treat our totals as a well-informed starting point, and confirm with a licensed electrician for medical equipment or panel work. The full sizing method is written up here.
Before you buy anything, read these
The four-step sizing method installers actually use: list must-run loads, separate running from starting watts, size for the biggest surge, then add headroom.
Extension cords, generator inlets, interlock kits, and transfer switches compared — with costs — and why backfeeding through a dryer outlet can kill a lineworker.
A $1,100 portable covers most outages; a $12,000 standby covers all of them without you touching anything. Where each one actually makes sense.
The one thing to know before your first outage
Generators run outside only, at least 20 feet from the house, exhaust pointed away — never in a garage, even with the door open. Carbon monoxide from portable generators kills roughly 70–80 people in the US every year, and every one of those deaths was preventable. Read the 5-minute safety guide.
Frequently asked questions
How do I figure out what size generator I need?
List the appliances that must run during an outage, add up their running watts, then add the single largest starting surge (the biggest gap between one appliance's starting and running watts) on top. Buy a generator whose running-watt rating is about 20–25% above your total so it isn't working flat-out. The calculator on this page does all of that math for you from published per-appliance figures.
What's the difference between running watts and starting watts?
Running watts are the continuous draw once an appliance is going. Starting watts are the brief surge — typically 2–3× the running draw — that motors and compressors pull for a second or two at startup. A generator must cover your total running load plus the largest single surge, or motors simply won't start.
What will a 2,000-watt generator run?
A refrigerator OR a small window AC, plus lights, a Wi-Fi router, phone and laptop chargers, and a TV — with care to let each motor start before adding the next load. It won't run a well pump, a central AC, or an electric water heater. For the classic fridge-freezer-furnace-fan storm kit, you want the 3,500–5,000-watt class.
Can I plug a generator straight into my house?
Not into a wall or dryer outlet — that backfeeds the grid and can kill a utility lineworker. The safe options are heavy-duty extension cords to individual appliances, or a professionally installed inlet with an interlock kit or transfer switch (roughly $400–$1,500 installed), which lets the generator feed your panel legally.
Do I need an inverter generator or a conventional one?
Inverters cost more per watt but run far quieter, sip fuel at partial load, and produce clean power that's safe for laptops and CPAPs — right for camping, RVs, and neighborhoods. Conventional open-frame units give maximum watts per dollar and are the value pick for essentials or whole-house backup through a transfer switch, if you can live with lawn-mower noise.