Power station for a sump pump: size and runtime
Storms that knock out power are the same storms that fill your sump pit. A sump pump is a motor, so two numbers matter: the start-up surge the station must be able to deliver, and how many hours the pump really runs.
Typical numbers
| Item | Typical running | Typical start-up surge |
|---|---|---|
| Sump pump, 1/3 HP | 800 W | about 2,400 W |
Typical values; the label on your pump wins. A 1/2 HP pump draws more.
Surge decides which stations qualify
If the station cannot supply the surge, it shuts off even with a full battery. So check the station's surge or peak rating against about 2,400 W for a 1/3 HP pump before looking at battery size.
Worked example
The pump only runs while water is being pumped out. In a wet storm, assume 10% of the day, about 2.4 hours: 800 W × 24 h × 0.10 = about 1,900 Wh a day. A 1,000 Wh battery (850 Wh usable) covers roughly 10 hours of that. A 2,000 Wh battery covers roughly 21 hours. Heavy inflow means more running time; a dry spell means far less, so treat this as a planning figure, not a promise.
Good to know
- Most sump pumps plug into a normal 120 V outlet. Hardwired pumps need an electrician.
- Dedicated battery-backup sump pump systems exist and may suit you better if the pump is your only concern.
- Recharging from solar during a multi-day storm is unreliable. Size the battery to carry the pump on its own.
Open the calculator with a sump pump filled in
Appliance figures are typical values, not measurements of your device: the label or a plug-in watt meter on yours wins. The sums assume 85% of a battery's rated capacity reaches your outlets (how the numbers work). We list no prices and have not hands-on tested any product.
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Check start-up surge against your station (soft-start tool).