What it draws
Sump Pump
The sump pump is the clearest example on this site of why surge matters more than capacity. It is a motor that starts under load, in a basement, during exactly the weather that takes the power out, and it is the load most likely to be refused by a battery that looks large enough on paper.
Typical draw, and the number that actually applies
A residential sump pump commonly draws somewhere between 500 and 1000 W while running. The nameplate on the pump housing is the figure that applies to yours, and pump sizes vary widely between houses.
Read the nameplate. It is usually a sticker on the back, inside a door, or on the power adapter, and the figure printed there is a maximum for that specific unit rather than a typical reading. Any range on this page is a starting point for arithmetic, not a substitute for that label.
- Running watts used here
- 800 W
- Duty share applied
- No honest figure
Why there is no hour figure on this page
This site publishes no runtime estimate for this load
- An earlier version of this page divided by a 10 percent duty share and produced about eleven hours. That number was worse than useless. It described a dry basement on a calm day, which is the one situation in which nobody needs a sump pump. In the weather that takes the power out, the pit refills as fast as it empties and the pump approaches continuous running, which moves the honest answer to somewhere near an hour — and even that assumes the pump starts at all, which its startup surge does not guarantee. A figure that swings by a factor of ten depending on an assumption the reader cannot check is not an estimate, so this site withholds it.
Every other device page on this site divides (1024 x 0.85) by an average draw and prints the result. That works when the duty share is stable enough to be worth stating. Here it is not, and printing a figure with a warning attached to it would still leave a figure on the page for somebody to plan around.
What belongs here instead is the name of the right product category and the right trade. A dedicated battery backup sump pump is a purpose-built device, sized to your pump and your pit, and it is installed by a licensed plumber. That is the answer to this problem. A power station is not.
Starting surge
This is the important one. A sump pump motor starts against a column of water already sitting on it, and the starting demand can be several times the running figure. A power station with a continuous rating above the pump's running wattage may still fault the instant the pump tries to start, because the peak demand exceeds what the inverter will supply. Whether a specific pump and a specific unit work together is not something this site can tell you, and the pump manufacturer and the power station manual are where that question belongs.
Duty cycle
A sump pump runs in short bursts when the pit fills rather than continuously. How often depends entirely on how much water is arriving, and that is the whole problem: the pump matters during the storm that took the power out, and during that storm it is not cycling occasionally, it is running close to continuously. There is no duty share that is honest across both conditions, so this site does not pick one.
How to get by without powering it
Every watt-hour you do not spend is one you still have. These are the moves that cost nothing.
- Talk to a licensed plumber about a dedicated battery backup sump pump. These are purpose-built for this job, sized to your pump and your pit, and they are the real answer rather than a workaround built out of a power station.
- Clear the discharge line and the pit before storm season, so the pump is not fighting a partial blockage on the night it matters.
- Know where the water goes if the pump stops, and move anything you care about off the basement floor before the season, not during the storm.
- Do not plan around a power station here at all. A pump that will not start, or that empties the battery in an hour, is worse than no plan, because decisions were made in the belief that there was one.
Where this sits in the sequence
No stage in this sequence covers this load
- No stage in this sequence covers running a sump pump from a portable battery. Two things defeat it at once: the starting surge may prevent the motor turning over at all, and in the conditions where the pump is needed it runs nearly continuously rather than in short bursts. A dedicated battery backup pump, sized and installed by a licensed plumber, is the actual answer to this problem.
It appears on this site as an example rather than as a recommendation. The section above is the honest answer, and the arithmetic higher up the page is why.
Related gear
Products live on the gear pages rather than here, because the decision on this page is about arithmetic and the decision there is about hardware.