What Size Generator Do You Need? Sizing by Appliance

Generator sizing has two numbers and most buying guides only give you one. Running watts keeps a load going. Starting watts gets it moving. A generator that comfortably runs your refrigerator all day may stall the moment the compressor kicks in.

Add the running watts of everything that must stay on, then add only the single largest starting surge on top. Motors rarely start at the same moment, and sizing as though they do buys a generator far bigger than you need.

Check a load before you size a generator

Change any box. The result updates as you type.

W
hours
USD/kWh
Cost per month
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—
Per hour
—
Per day
—
Per year
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kWh per day
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Planning estimate. The rate box is prefilled with a regional average; the figure on your own bill is the one that matters. Power is draw while running, not while switched on.

Sizing for every appliance

Air quality

ApplianceRunning WStarting WMin generator
Dehumidifier5001,5002,000 W
Air purifier50602,000 W
Humidifier40402,000 W

Cleaning

ApplianceRunning WStarting WMin generator
Vacuum cleaner1,4002,8003,500 W

Cooling

ApplianceRunning WStarting WMin generator
Central air conditioner3,50010,50012,000 W
Portable air conditioner1,1003,3003,500 W
Window air conditioner9002,7003,500 W
Evaporative cooler3006002,000 W
Box fan751132,000 W
Ceiling fan60902,000 W
Tower fan50752,000 W

EV

ApplianceRunning WStarting WMin generator
Level 2 EV charger7,2007,20012,000 W

Electronics

ApplianceRunning WStarting WMin generator
Gaming PC4004002,000 W
Game console1601602,000 W
Desktop computer1501502,000 W
Television90902,000 W
Laptop60602,000 W
Soundbar with subwoofer40402,000 W
Computer monitor30302,000 W
Cable box / DVR25252,000 W
Printer20202,000 W
Wi-Fi router10102,000 W
Home security panel662,000 W
Streaming box (Roku, Apple TV, etc)442,000 W
Smart speaker332,000 W
Cordless phone base332,000 W

Fitness

ApplianceRunning WStarting WMin generator
Treadmill9001,8002,000 W

Heating

ApplianceRunning WStarting WMin generator
Garage heater5,0005,0007,500 W
Air-source heat pump3,0009,0009,500 W
Space heater1,5001,5003,500 W
Electric fireplace1,5001,5003,500 W
Electric baseboard heater1,5001,5003,500 W
Mini-split heat pump9001,8002,000 W
Electric blanket1001002,000 W

Kitchen

ApplianceRunning WStarting WMin generator
Electric oven2,4002,4003,500 W
Dishwasher1,8002,7003,500 W
Electric stove burner1,5001,5003,500 W
Air fryer1,5001,5003,500 W
Electric kettle1,5001,5003,500 W
Toaster1,2001,2002,000 W
Microwave oven1,0001,2002,000 W
Electric pressure cooker1,0001,0002,000 W
Coffee maker9009002,000 W
Chest freezer2006002,000 W
Slow cooker2002002,000 W
Refrigerator1504502,000 W

Laundry

ApplianceRunning WStarting WMin generator
Electric clothes dryer3,0003,0005,000 W
Washing machine5001,5002,000 W

Lighting

ApplianceRunning WStarting WMin generator
Incandescent light bulb60602,000 W
LED light bulb992,000 W

Other

ApplianceRunning WStarting WMin generator
Aquarium heater2002002,000 W
CPAP machine40402,000 W

Outdoor

ApplianceRunning WStarting WMin generator
Pool pump1,5004,5005,000 W
Hot tub1,5003,0003,500 W
Sump pump8002,4003,500 W
Well pump7502,2503,500 W

Personal care

ApplianceRunning WStarting WMin generator
Hair dryer1,8001,8003,500 W

Water heating

ApplianceRunning WStarting WMin generator
Electric tankless water heater18,00018,00022,000 W
Electric water heater4,0004,0007,500 W
Heat pump water heater5001,5002,000 W

The mistake that kills people

Running a cord from a generator into a wall outlet, sometimes called a suicide cord, backfeeds electricity into the house wiring and out to the utility line. Line crews working on what they believe is a dead circuit have been killed this way. A transfer switch or breaker interlock, installed by an electrician, is the only correct connection.

The second common error is carbon monoxide. Generators must run outdoors, well away from windows and never in a garage, even an open one. CO from a portable generator kills people every storm season.

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