How many watts does a sump pump use?
A typical sump pump uses 475–750 watts when running and draws 4–6.3 amps at 120 volts.
Sump pump watts, amps and circuit
| Running watts | 475–750 W |
|---|---|
| Voltage | 120 V |
| Running amps | 4–6.3 A |
| Circuit | standard 120 V outlet |
Also called: basement sump pump.
Sump pump watts by size and type
| Size or type | Running watts, W | Volts, V | Amps, A | Starting watts, W |
|---|---|---|---|---|
| Sump pump | 475–750 | 120 | 4–6.3 | — |
| 1/3 HP | 475 | 120 | 4 | — |
| 1/2 HP | 550–750 | 120 | 4.6–6.3 | — |
What size generator runs a sump pump?
A sump pump needs a generator that supplies at least 750 running watts. Starting a sump pump takes a short surge of several times its running watts, and the surge is not listed here: size the generator from the locked-rotor amps (LRA) on the nameplate or the maker's generator guidance, not from the running watts.
How long a portable power station runs a sump pump
| Battery capacity, Wh | At 750 W, h | At 475 W, h |
|---|---|---|
| 500 | 0.6 | 0.9 |
| 1,000 | 1.1 | 1.8 |
| 2,000 | 2.3 | 3.6 |
| 3,600 | 4.1 | 6.4 |
A 500 Wh portable power station runs a sump pump drawing 750 W for about 0.6 hours at 85% inverter efficiency. Runtime = capacity × 85% ÷ watts; the 85% efficiency is an assumption. The power station's AC output must be at least 750 W.
What it costs to run a sump pump
Running a sump pump at 613 W, the middle of its 475–750 W range, for one hour a day uses 223.7 kWh a year. That costs about $40 a year at $0.18 per kWh, the US average residential price for August 2026.
Your bill's total ÷ kWh used. 0.18 is the US residential average.
- Per day
- $0.11
- Per year
- $40
- Energy per day
- 0.61 kWh
- Energy per month
- 18.6 kWh
How it is calculated
- kWh per day = 613 W × 1 h ÷ 1,000 = 0.613
- Per month = 0.613 kWh × 30.4 days × $0.18 = $3.36
What affects sump pump power use
Motor horsepower sets the running watts, and the motor needs a brief surge to start: Little Giant lists a starting current of 12 to 14.5 A for these pumps against 5 to 6.5 A while running. The pump runs only when the float switch trips, so it may sit idle for weeks and then run often in heavy rain.
How the amps are calculated
Amps = watts ÷ volts. For 750 W at 120 V that is 6.3 A. The 475–750 W range covers typical models; the nameplate on a sump pump gives the exact figure.