Use case
Backup power for a sump pump during a storm
Storm outages and sump-pump duty go together. The pump's startup surge is the number to size around — undersize it and your basement floods at the worst moment.
Running
1,260W
Peak surge
2,540W
Recommend
3,500W
The sump pump (1/3 hp) drives the peak here, surging when it starts. Sizing for the running total plus that single largest surge — not the sum of every surge — gives a realistic 3,500W (3.5kW) recommendation.
Typical loads for a sump pump during a storm
| Load | Running | Starting |
|---|---|---|
| Sump pump (1/3 HP) | 800W | 2080W |
| Refrigerator | 160W | 480W |
| Household lights (LED) | 200W | 200W |
| Phone/laptop charging | 100W | 100W |
Size your exact setup
Common questions
What size generator do I need for a sump pump during a storm?
For this typical load set, about a 3,500W (3.5kW) class covers it — that's 1,260W running plus the largest startup surge (from the sump pump (1/3 hp)), with a 20% margin.
Can I run more than this?
Yes — this is a representative set. Add or remove loads in the load sizer to match your exact situation and get an updated number.