How to Size a Standby Generator for Your Home

Start With What You Need to Power

The right generator size comes down to one question: what do you want to keep running when the grid goes down?

Most homeowners fall into one of three categories:

• Essential circuits — lights, refrigerator, sump pump, internet, and a few outlets.
• Most of the home — adds central A/C, well pump, and major appliances.
• Whole home — everything, including electric range, dryer, and EV charging.

The Big Draws

Air conditioning is almost always the largest single load in a home. A single central A/C unit can demand 3–5 kW on startup. Add a well pump, electric water heater, or EV charger and your requirement climbs quickly.

A Simple Rule of Thumb

As a starting point, many single-family homes land between 14 kW and 26 kW depending on size and coverage. But rules of thumb only get you close — a proper load calculation is what locks in the right unit and avoids overspending on capacity you'll never use.

Our free online estimate walks you through your home profile and returns a sized recommendation in about two minutes.