Runtime evidence · sourced load
A sump pump draws 800 W while running, and 2,000 W at startup. 1 station clears the capacity, inverter, and startup checks at that load.
By the BatteryRank Engineering Team
01 · Runtime ladder
Nominal capacity × depth of discharge × inverter efficiency ÷ sourced average draw.
| Capacity class | Estimated runtime | Evidence |
|---|---|---|
| 300 Whstep 1 | 0.3 hr | Sump pump (1/3 HP) load · 2026-07-06 |
| 500 Whstep 2 | 0.5 hr | Sump pump (1/3 HP) load · 2026-07-06 |
| 1,000 Whstep 3 | 1 hr | Sump pump (1/3 HP) load · 2026-07-06 |
| 2,000 Whstep 4 | 1.9 hr | Sump pump (1/3 HP) load · 2026-07-06 |
These are comparison projections, not a promise. Temperature, inverter behavior, cycling, and the individual station's measured delivered capacity can change real runtime.
02 · Reading the numbers
A sump pump is the hardest load on this site for its size. It draws 800 W while pumping but demands roughly 2,000 W for the fraction of a second the motor breaks away from standstill, and it does that every time the float switch closes. During the storm that makes you need it, that can be several starts an hour for hours.
Buying for the running watts. An 1,000 W station matches the pump on paper and fails on the first start. The second mistake is treating total energy as the constraint: the pump runs in short bursts, so a modest battery covers a long night — it is the inverter surge rating that eliminates almost every station in our catalog, not the capacity.
Our figures describe a one-third-horsepower pedestal-style pump. Half-horsepower and above draw proportionally more, and an old pump with worn bearings draws more still. The pump nameplate on your own basin is the number to use, and it is the one figure worth walking downstairs to read before you buy anything.
03 · Passing stations
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Best all-round fit
Why it fits
79.7 BatteryRank score — the highest of any station that fits this plan
Main compromise
No measured compromise across 1 eligible models
This ordered data view is separate from the single recommended buying strategy above.
Runtime uses each linked model's sourced capacity and output data; open its dossier for provenance.
Solar effect
Computed with this model's sourced solar-input limit and BatteryRank's published harvest assumptions. Check the solar method → · Model sources →
04 · Evidence record