Generator Size for Sump Pump, Fridge, and Lights
Calculate the generator needed to run a sump pump, refrigerator, and lights — approximately 2,500 running watts with a 1,500W sump pump surge.
How to use this tool
- List the appliances you'll run at the same time and their running watts.
- Enter the total running watts of that list.
- Find the single appliance with the biggest starting surge and enter it.
- Add an optional safety margin for headroom or future loads.
- Read the running and starting watts your generator must meet or exceed.
Size a generator for your most critical outage loads: sump pump, refrigerator, and lights.
Frequently asked questions
- What size generator do I need for my house?
- Add the running watts of everything you'll power at once, then add the largest single starting surge. Essentials (fridge, lights, a few outlets, furnace fan) often need 3,000–5,000 running watts; whole-home backup with AC and well pump can need 7,500–10,000 or more.
- Why are starting watts higher than running watts?
- Appliances with electric motors draw a brief inrush current at startup, often two to three times their running draw. The generator must supply that surge momentarily, so its starting rating must exceed the running total plus the biggest surge.
- Should I add a safety margin?
- A 10–25% margin on the running load is prudent so the generator isn't always at full output and you have room for added loads. This tool's safety-margin field lets you build that headroom into the result.