What size power station runs a sump pump?
A 1/3 HP sump pump can draw about 800 W while it pumps and 1,600 W for a moment as it starts. One hour of pumping a day takes about 1,046 Wh of power station capacity. How many hours it pumps depends on how much water comes in, not on the pump.
The numbers
Champion's generator wattage chart lists a 1/3 HP sump pump at 500–800 W running and 1,000–1,600 W starting, and a 1/2 HP pump at 800–1,050 W running and 1,300–2,150 W starting. We use the upper ends: 800 W / 1,600 W and 1,050 W / 2,150 W. A sump pump draws close to its full running watts whenever it runs, so we use the running watts as the average while pumping. The question is how many hours a day it runs.
That depends on how fast water enters the pit. The pump switches on when the water reaches its float's on point and off when the pit is drawn down (Zoeller's Model 53, for example, switches on at 7-1/4 in and off at 3 in). Pumping time per day is roughly the gallons that flow in that day divided by the pump's flow rate at your discharge height. For example, 2,000 gallons at 30 gallons a minute is about 67 minutes of pumping. Inflow ranges from almost nothing in dry weather to nonstop running when water comes in faster than the pump can move it. Enter total pumping time per day in the calculator. The 1 h default is only a placeholder.
| Scenario | Wh/day from battery | Min capacity Wh | Cont. W | Surge W |
|---|---|---|---|---|
| 1/3 HP, 1 h pumping per day | 941 | 1,046 | 800 | 1,600 |
| 1/3 HP, 2 h per day (wet spell) | 1,882 | 2,092 | 800 | 1,600 |
| 1/3 HP, 4 h per day (heavy rain) | 3,765 | 4,183 | 800 | 1,600 |
| 1/3 HP, 1 h per day, 3 days, no recharge | 941 | 3,137 | 800 | 1,600 |
| 1/3 HP running nonstop, 24 h | 22,588 | 25,098 | 800 | 1,600 |
| 1/2 HP, 1 h per day | 1,235 | 1,373 | 1,050 | 2,150 |
| 1/2 HP, 4 h per day | 4,941 | 5,490 | 1,050 | 2,150 |
| 1/3 HP 2 h + top-freezer fridge 24 h | 3,043 | 3,381 | 1,200 | 2,000 |
Assumptions: 85% inverter efficiency, 90% of rated capacity usable, no extra margin. Both are planning values, not measurements, and you can change them in the calculator.
Models in our table that fit a 1/3 HP pump running 1 h a day
Fits (cheapest first):
- BLUETTI AC180: 1,152 Wh, 1,800 W / 2,700 W surge, $499 (checked 2026-10-21). Runtime at this load ≈ 26.4 h.
- Jackery Explorer 1000 v2: 1,070 Wh, 1,500 W / 3,000 W surge, $519 (checked 2026-10-21). Runtime at this load ≈ 24.6 h.
- Anker SOLIX C1000: 1,056 Wh, 1,800 W / 2,400 W surge, $599.99 (checked 2026-10-21). Runtime at this load ≈ 24.2 h.
- Jackery Explorer 2000 v2: 2,042 Wh, 2,200 W / 4,400 W surge, $899 (checked 2026-10-21). Runtime at this load ≈ 46.9 h.
- Anker SOLIX C2000 Gen 2: 2,048 Wh, 2,400 W / 4,000 W surge, $999.99 (checked 2026-10-21). Runtime at this load ≈ 47.0 h.
- EcoFlow DELTA 2 Max: 2,048 Wh, 2,400 W / 4,800 W surge, $1,049 (checked 2026-10-21). Runtime at this load ≈ 47.0 h.
- Anker SOLIX F3800: 3,840 Wh, 6,000 W / 9,000 W surge, $2,199.99 (checked 2026-10-21). Runtime at this load ≈ 88.1 h.
- EcoFlow DELTA Pro 3: 4,096 Wh, 4,000 W / 8,000 W surge, $2,799 (checked 2026-10-21). Runtime at this load ≈ 94.0 h.
Closest that fall short:
- Anker SOLIX C1000 Gen 2: 1,024 Wh, 2,000 W / 3,000 W surge, $549.99 (checked 2026-10-21). Runtime at this load ≈ 23.5 h. Short on capacity.
- EcoFlow DELTA 3: 1,024 Wh, 1,800 W / 3,600 W surge, $629 (checked 2026-10-21). Runtime at this load ≈ 23.5 h. Short on capacity.
- EcoFlow DELTA 3 Plus: 1,024 Wh, 1,800 W / 3,600 W surge, $719 (checked 2026-10-21). Runtime at this load ≈ 23.5 h. Short on capacity.
Surge is the first filter. Even with enough Wh, a station whose surge rating is below the pump's starting draw may shut off when the pump kicks on. In our table, these are rated below 1,600 W for a 1/3 HP pump: Jackery Explorer 300 v2 (600 W), EcoFlow RIVER 3 Plus (1,200 W) and BLUETTI AC70 (1,500 W). For a 1/2 HP pump (2,150 W start), the same models fall short, and the lowest-rated model that clears it is the Anker SOLIX C1000 at 2,400 W. These are the brands' published surge ratings, so leave some headroom.
What changes the answer
- Your pump's nameplate. Chart figures are typical, not your pump. Zoeller's Model 53, a 3/10 HP pump, is rated 9.7 A at 115 V. Volts × amps gives about 1,116 VA, which is more than the 800 W chart figure. Real watts are at or below the VA figure, so the nameplate is the safer number to plan with. A plug-in watt meter will show your pump's actual running watts.
- Pumping hours are the big unknown. They can go from minutes a day to most of the day during a storm, and a storm that brings heavy rain can also knock out power. A battery sized for a dry day can run flat on a wet one. Running nonstop, a 1/3 HP pump needs more than any single station in our table. If you can, time how long your pump runs per cycle and how often it cycles during heavy rain.
- Idle draw. The station's AC output has to stay on all day so the pump can start whenever the float trips. An inverter uses some power even when nothing is running. The calculator doesn't include this, so add margin or check the station's manual.
- Don't rely on a battery alone for flood protection. A power station only buys time. When it's empty, the pit fills. Plan how you'll recharge it (solar, car, generator), and consider a dedicated battery backup pump, a water alarm or a generator if a flooded basement would be costly. Plug the pump straight into the station or into a heavy-duty cord rated for its draw.
Open this in the calculator. Change the hours, efficiency or days there.
Sources: Champion wattage chart (Sump pump 1/3 HP 500–800 W / 1,000–1,600 W); Champion wattage chart (Sump pump 1/2 HP 800–1,050 W / 1,300–2,150 W); Zoeller Model 53 product page (3/10 HP; 4.8–9.7 A (230 V / 115 V); up to 43 GPM; max head 19.25 ft); Zoeller Model 53 sales sheet FM2958 (auto on/off points 7-1/4 in / 3 in).