What Size Inverter to Run a Sump Pump?

Answer
1,500 W pure sine · 3,000 W surge

A typical sump pump draws about 1,000 W. Size the inverter for at least 1,500 W continuous and 3,000 W surge to handle startup. At 12 V it pulls about 93 A from the battery.

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W
Everything on at the same time.
W
Largest motor only: fridge ≈ 1,000–2,000 W.
%
Inverter size
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How we calculated this

    For estimating and educational purposes only. Results are approximate and are not a substitute for a licensed professional, the manufacturer's instructions or your local code. Disclaimer

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    Why this size

    A 1/2 hp sump pump; motors need a large starting surge. We size the continuous rating at 125% of running watts and check that the surge rating (usually about twice the continuous rating) covers the startup.

    Value
    Running watts1,000 W
    Surge needed3,000 W
    Battery current at 12 V93 A
    Battery current at 24 V46 A

    Frequently asked questions

    How long will a 100Ah battery run a sump pump?

    About 1.0 hours from a 12 V 100 Ah lithium battery at a steady 1,000 W (less for cycling appliances, more for intermittent ones).

    Do I need a pure sine wave inverter?

    Yes for motors, compressors, medical devices and modern electronics.

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