Homeowner tools

What size generator do I need?

Explore the power you want to protect. Build a preliminary load estimate, then let a professional verify the complete picture.

What would you like to keep running?

Start with an example, then adjust quantities and wattages to match your equipment. These are not measured values for your property.

Use whole quantities from 0–20 and watts from 0–100,000. Selected items need running watts greater than zero. If a load is unknown, use the unknown-load option below.

Refrigerator / freezerExample household unitQtyRunning WExtra start W

Lighting60 W equivalent load per item; edit actual wattsQtyRunning WExtra start W

Wi-Fi routerExample modem / routerQtyRunning WExtra start W

Furnace fan½ HP example; not electric heatQtyRunning WExtra start W

Sump pump½ HP exampleQtyRunning WExtra start W

Well pump⅓ HP exampleQtyRunning WExtra start W

Central air conditioning24,000 BTU example; verify your systemQtyRunning WExtra start W

Electric water heaterExample tank heaterQtyRunning WExtra start W

Electric cooking elementOne 8-inch element, not a complete rangeQtyRunning WExtra start W

Other known loadEnter the actual running and extra starting wattsQtyRunning WExtra start W

Explore all selected motor loads starting together (more conservative).I have additional or unknown loads that still need assessment.

How the estimate works

We add the running watts of selected loads and the largest additional motor-starting demand. If you select simultaneous starts, we add all selected extra starting demand instead. The upper end adds a 25% planning allowance; that allowance is our illustrative scenario, not a manufacturer sizing rule.

Examples come from Generac’s appliance worksheet (pages 26–27). Check your equipment documentation for actual values. Fuel rating, motor starting kVA, voltage, load management and code requirements can change the final specification. This estimator is a planning aid; a technician confirms sizing on site.