Generator Size Calculator

It depends on whether you want backup for just the essentials or closer to whole-home. A fridge, freezer, lights, and some electronics usually run fine on 3,000 to 5,000 watts. 7,500 to 10,000 watts covers most essential circuits including a well pump or window AC. Whole-home standby units typically start around 14,000 watts. The calculator adds up your selected appliances and suggests a size above that total with headroom.

You add them, but only for the single biggest motor start. Anything with a motor (fridge, sump pump, AC compressor) spikes 2 to 3 times its running wattage for a few seconds at startup. Only one motor typically starts at a time, so the generator needs to handle the largest single surge plus the running load of everything already connected. That's what the calculator does automatically when you check appliances.

The fastest source is the nameplate sticker on the back or bottom of the appliance. It shows either watts directly, or volts × amps that you multiply (120 V × 5 A = 600 W). For cycling devices like refrigerators, a plug-in energy monitor like a Kill A Watt gives the most accurate real-world draw. If you can't find the sticker, the calculator's built-in defaults are reasonable averages for each appliance type.

Yes. If you don't need every appliance running simultaneously, you can stagger them and pick a smaller unit. Run the fridge for a few hours, then switch to the microwave, then back. A generator paired with a transfer switch and load management module does this automatically, shedding non-critical circuits when a well pump or AC kicks on. Staggering works best for outages over 24 hours when you have time to plan the rotation.

For smaller loads under about 4,000 watts and anything with electronics (laptops, TVs, medical equipment, phones), an inverter generator delivers cleaner power and runs much quieter. For larger loads above 5,000 watts or heavy motor starts like a well pump, conventional generators usually cost less per watt and handle surges better. Many homes end up with an inverter for everyday use and a larger conventional unit ready for long outages.

A 7,500-watt generator covers the essentials in most homes: refrigerator, freezer, furnace blower, lights, sump pump, microwave, and a window AC, with headroom to spare. It usually won't carry a central AC, electric range, electric dryer, or a heat pump at the same time. See what a 7,500 watt generator can run for a full appliance breakdown.