What Size Generator Do I Need for a Well Pump?
A typical 1/2 HP shallow or jet well pump needs roughly 900-1,500 running watts and 1,500-3,000 starting watts. A deep-well submersible pump (3/4-1.5 HP) can need 1,500-2,500 running watts and anywhere from 2,000 to 6,000 starting watts — the widest range of any common household appliance, because submersible motors vary so much by lift depth and horsepower.
Why "well pump" isn't one number
A shallow jet pump sitting above ground and a deep-well submersible pump lowered hundreds of feet down a well casing are built very differently, even though both get called "well pumps." The submersible design generally needs a stronger motor to lift water farther, which is why its starting-watt range in the Startup Watt Index runs so much wider (2,000-6,000W) than the shallow pump's (1,500-3,000W).
Finding your pump's real number
The most reliable path is your pump motor's nameplate: running amps and voltage give you running watts (amps × volts), and a listed locked-rotor amps (LRA) figure, where present, gives a much more precise starting-watt estimate than the horsepower-based range above. Absent a nameplate LRA, use the range as a planning estimate and size toward the higher end if you're unsure of your pump's exact horsepower or lift depth.
This page gives typical planning ranges compiled from published generator-sizing guidance, not a guaranteed figure for your specific well pump — check the motor's nameplate where possible.
Frequently Asked Questions
For a typical 1/2 HP shallow/jet well pump, plan for roughly 900-1,500 running watts and 1,500-3,000 starting watts — a generator with at least 2,000W running and 3,200W surge is a reasonable minimum. Deep-well submersible pumps (3/4-1.5 HP) can need 1,500-2,500 running watts and 2,000-6,000 starting watts.
Submersible deep-well pumps have to lift water further and often use larger motors, so their starting surge varies more than almost any other household appliance — a shallow 1/2 HP jet pump and a deep 1.5 HP submersible are very different loads even though both are called 'well pumps.'
Check the motor's nameplate for running amps and voltage (watts = amps x volts) and, if listed, a locked-rotor amps (LRA) figure for a more precise starting-watt estimate. Absent a nameplate LRA figure, use the horsepower-based range as a planning estimate.
Yes, if you size for BOTH running watts added together and a surge capacity that covers whichever single appliance's starting watts is larger. A 3,000-4,000W continuous generator with adequate surge capacity can typically cover a well pump and a refrigerator together, but always check your specific pump's nameplate.
No — they're different loads. Sump pumps are generally smaller (1/3-1/2 HP) with somewhat lower running watts but can still have a wide starting-watt range. See the full Startup Watt Index for both side by side.