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What Size Generator Do I Need?

Select the appliances you absolutely must run during a power outage. Our calculator instantly determines your required running and starting watts.

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Starting Watts Peak surge power
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Add items to see the generator size you need.

How to Choose the Right Generator for Your Home (USA Guide)

From Florida hurricanes and Texas winter storms to California rolling blackouts, having a reliable home backup power source is essential for American homeowners. The FEMA recommended generator size depends entirely on what you consider "critical." Buying a generator that is too small means overloaded circuits, while buying one that is too large wastes money on fuel. Understanding how to calculate your power needs for standard USA 120V/240V appliances is the first step.

Starting Watts vs. Running Watts Calculator

The most common mistake when sizing a generator for a house is only looking at "Running Watts." Here is the crucial difference:

To calculate what size generator you need to run a refrigerator, freezer, and AC, our calculator adds up the total Running Watts and accounts for the highest single Starting Watt requirement.

Best Backup Power Options for USA Outages

Portable Power Stations

Battery banks (like EcoFlow or Jackery). Silent, EPA-friendly, and safe for indoor use. Perfect for apartments or keeping phones, internet routers, and CPAP machines running during localized outages.

Inverter Generators

Gas/propane powered and highly popular in hurricane zones. They produce "clean" electricity safe for sensitive electronics. Excellent for running a fridge, fan, and TV simultaneously. (e.g., Honda, Champion).

Portable Home Generators

Loud but incredibly powerful. Required if you need to connect to a manual transfer switch to run 240V appliances like well pumps, water heaters, or central AC. Must be run safely outdoors away from windows.

Further Reading & Guides