What Size Generator Runs a Sump Pump? (1/3, 1/2, 3/4 HP Chart)
The list, with sourced watts
| Appliance | Running watts | Starting (surge) |
|---|---|---|
| Sump pump (1/3 HP) | 800 | 2,100 |
| Sump pump (1/2 HP) | 1,050 | 2,200 |
| Refrigerator/freezer (standard household) | 1,000 | 2,200 |
The arithmetic, both ways
Full kit (every item below, at once): 2,850W running + 1,300W largest surge = 4,150W → × 1.2 = ~5,000W
Generators for the sump pump alone
Spec: official_press
As an Amazon Associate, needwatts.com earns from qualifying purchases. Links below are affiliate links — this never affects our wattage math or which units we list.
See Honda EU3200i on Amazon →Spec: manufacturer_pdf
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See Generac iQ3500 (7127/7723) on Amazon →Spec: manufacturer
As an Amazon Associate, needwatts.com earns from qualifying purchases. Links below are affiliate links — this never affects our wattage math or which units we list.
See Champion 201531 (4500W Dual Fuel Inverter, CO Shield) on Amazon →Covering the full kit (~5,000W)
Spec: manufacturer
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See Westinghouse WGen5300 on Amazon →Spec: authorized_dealer
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See Honda EU7000iS on Amazon →Adjust this list in the calculator →
How many watts do I need for a sump pump?
800 running watts with 2,100W available at startup; ~2,600W rated recommended. The full kit on this page needs ~5,000W.
Why do starting watts matter?
Motor-driven appliances (fridges, pumps, AC compressors) briefly draw 2–4× their running watts at startup. A generator must cover running load plus the largest single surge, or the motor stalls and breakers trip.
Is a bigger generator always better?
No — oversized open-frame units burn more fuel and run louder. Size to your real list with ~20% headroom.
Sources
- Wattage Worksheet '3R0WATTGUIDE' (generator reference guide, Home Depot-hosted PDF) (vendor)
- A-iPower Wattage Chart (Sam's Club-hosted PDF) (vendor)
- Howell-Oregon Electric Cooperative generator sizing chart (utility)
- Champion Power Equipment 'Choosing a Generator' wattage flyer (manufacturer)
Figures are conservative sizing values chosen from the range these sources report. Your appliance's nameplate is authoritative.