Generator Appliance Load Builder
Build a list of appliances you want to operate during an outage and estimate the generator running watts and starting watts you need.
Add an Appliance
Starting watts are the total watts an appliance may require briefly when its motor or compressor starts. Appliances without a startup surge can use the same value for running and starting watts.
Appliances to Run
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| Appliance | Qty. | Running | Starting |
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Generator Planning
The standard estimate assumes the largest motor starts while the other selected appliances are already running. Choose simultaneous startup for a more conservative estimate.
Generator Load Estimate
Wattage varies by model, motor size, age, operating conditions, and startup behavior. Verify the nameplate or manufacturer specifications for every appliance.
What Size Generator Do I Need?
A generator must provide enough continuous running power for the appliances operating at the same time and enough temporary surge power when a motor or compressor starts. Refrigerators, freezers, sump pumps, furnace blowers, well pumps, and air conditioners commonly require startup power above their normal running wattage.
Running Watts Versus Starting Watts
Running watts, sometimes called rated watts, are the power a generator can continuously supply. Starting watts, sometimes called surge or peak watts, are available briefly to start appliances with motors or compressors.
Generator Size for a Refrigerator and Freezer
Refrigerators and freezers usually consume moderate power while running but can require several times their running wattage when the compressor starts. Use the appliance nameplate or manufacturer specifications whenever possible instead of relying only on a general wattage estimate.
Generator Size for a Sump Pump
Sump-pump power requirements depend heavily on motor horsepower. A sump pump may have a substantial startup surge, making the generator’s starting-watt rating especially important. A working sump pump may also be a priority load during severe weather and power outages.
Generator Size for a Furnace Blower
A gas or propane furnace still requires electricity for its blower, controls, and ignition system. Furnace-blower wattage varies by equipment. Connecting a furnace to a portable generator may require an approved transfer method installed according to electrical codes.
Why Include a Capacity Buffer?
Continuously operating a generator at its maximum rating leaves little room for changing loads, unexpected startup surges, or future equipment. The planning buffer increases the recommended rating above the estimated load.
Generator Safety
Never operate a fuel-powered generator indoors, in a garage, in a basement, or near doors, windows, or vents. Generator exhaust contains carbon monoxide, which can be deadly.
Never connect a portable generator directly to household wiring through a wall outlet. This dangerous practice can backfeed utility lines. Use properly rated cords or an approved transfer switch or interlock installed by a qualified electrician.
Planning Estimate Only
This tool provides an approximate generator load estimate. It does not replace appliance documentation, generator manufacturer guidance, electrical codes, or evaluation by a qualified electrician.