What size generator do I need for my house?
In an outage, the priorities are keeping food cold, the heat or AC on and the sump pump running. Pick the appliances you want to back up to get the minimum generator size, safety margin included.
Updated
1. Pick your appliances
Choose how many of each appliance you want to run and how many hours a day they run. Wattages are typical values: check the label on your own appliances.
Refrigerator
700 W running · 2,200 W starting
0 / 2Chest freezer
500 W running · 1,500 W starting
0 / 2Microwave (1,000 W)
1,000 W running · 1,000 W starting
0 / 10Coffee maker
1,000 W running · 1,000 W starting
0 / 10Window AC (10,000 BTU)
1,200 W running · 3,600 W starting
0 / 3Central AC (24,000 BTU)
3,800 W running · 11,500 W starting
0 / 1Furnace blower (1/2 HP)
800 W running · 2,350 W starting
0 / 1Space heater
1,500 W running · 1,500 W starting
0 / 3Electric water heater
4,000 W running · 4,000 W starting
0 / 1Sump pump (1/2 HP)
1,050 W running · 2,150 W starting
0 / 2Well pump (1/2 HP)
1,000 W running · 2,100 W starting
0 / 1LED lights (whole house)
100 W running · 100 W starting
0 / 10TV (55")
150 W running · 150 W starting
0 / 10Wi-Fi router + modem
20 W running · 20 W starting
0 / 10Laptop
60 W running · 60 W starting
0 / 10Mini fridge
100 W running · 300 W starting
0 / 2Air fryer
1,500 W running · 1,500 W starting
0 / 10Toaster
1,000 W running · 1,000 W starting
0 / 10Toaster oven
1,200 W running · 1,200 W starting
0 / 10Slow cooker
250 W running · 250 W starting
0 / 10Electric stove (one 8" burner)
2,100 W running · 2,100 W starting
0 / 10Oven (electric)
2,400 W running · 2,400 W starting
0 / 10Dishwasher
1,500 W running · 1,500 W starting
0 / 10Washing machine
1,150 W running · 2,250 W starting
0 / 10Clothes dryer (electric, 240 V)
5,400 W running · 6,750 W starting
0 / 10Heat pump (3 ton)
3,500 W running · 9,000 W starting
0 / 10Portable AC (8,000 BTU)
900 W running · 2,700 W starting
0 / 2Dehumidifier (50 pint)
600 W running · 1,200 W starting
0 / 10Box fan
100 W running · 100 W starting
0 / 3Ceiling fan
75 W running · 75 W starting
0 / 4Electric blanket
100 W running · 100 W starting
0 / 2Hair dryer
1,500 W running · 1,500 W starting
0 / 10Vacuum cleaner
1,000 W running · 1,500 W starting
0 / 10Desktop computer
150 W running · 150 W starting
0 / 10Gaming PC
450 W running · 450 W starting
0 / 10Computer monitor
30 W running · 30 W starting
0 / 3PS5
200 W running · 200 W starting
0 / 10
2. Your result
We add up the running watts, then add the single largest starting surge (motors never all start at the same second).
Recommended generator size
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Add at least one appliance to see your result.
- Running watts
- 0 W
- Starting peak
- 0 W
- Energy used per day
- 0 Wh
Power source
Frequently asked questions
How big a generator do I need to run a house?
The essentials (fridge, freezer, sump pump, furnace blower, lights and internet) usually fit a 5,000 to 7,500 W generator once starting surge and margin are counted. Central air conditioning changes the picture: a 2-ton unit alone can need over 11,000 starting watts. Add your own appliances above to get your number.
Can I run a generator indoors or in the garage?
No, never. The CDC reports more than 400 deaths from accidental carbon monoxide poisoning in the US each year, and the CPSC counts about 85 deaths a year from portable gasoline generators alone. The CPSC says to run a generator outside only, at least 20 feet from the house, with the exhaust pointed away from doors, windows and vents.
Why are starting watts higher than running watts?
Anything with a motor or compressor (fridge, AC, pumps) draws 2 to 3 times its running watts for a second or two when it starts. The calculator adds the single largest surge, because in practice motors don't all kick on at the same moment.
Why add a 20% safety margin?
A generator or inverter running at 100% all the time runs hot, wears faster and trips on the smallest surge. Aiming for about 80% of rated output leaves room for a forgotten appliance or a real draw higher than the label.
What's the difference between watts (W) and watt-hours (Wh)?
Watts measure power at a given moment: they size the generator or inverter. Watt-hours measure energy over time: they size the battery. A 60 W CPAP used for 8 hours uses 480 Wh.