What size generator do I need for a well pump?

The motor plate and a 240 V receptacle decide the generator. Household loads share the running watts; they do not each add a second surge.

Quick sizing question: what size generator for a well pump.

Generator size by pump horsepower

Do not shop from an unsourced horsepower table. Read horsepower, voltage, and locked-rotor amps on the plate, then open the sourced well-pump page for the Champion bands and the calculator for the rest of the house.

Why surge, not running watts, picks the generator

The pump is usually the largest single surge in a home backup plan. The generator can run near its rated watts continuously, but it still has to clear that one startup on top of everything already running. If the plate lists locked-rotor amps, size to that figure. The method, without a watt table, is on the well pump watts guide.

Two traps that send generators back

No 240 V outlet. Many deep-well submersibles are 240 V. A generator with only a 120 V receptacle will not start that pump. Confirm the receptacle matches the plate before you buy.

Stall on startup. If the generator bogs when the pump kicks in, the surge budget was exceeded. Fixes, cheapest first: staged startup (pump alone, then other loads), a pump soft-start kit, or a larger generator.

The pick

Pick the class the calculator prints after you enter the plate and the other loads. A soft-start kit is the alternative when the larger motor is the problem. Do not buy from a horsepower slogan.

FAQ

Can I run my well pump off a battery/inverter instead?

Yes, but the pump sizes the system. The inverter's surge rating has to clear the locked-rotor figure on the motor plate. The battery bank sizer handles the bank once you know that inverter.

How long will a generator run a well pump per day?

The pump runs when the pressure tank calls for water, not all day. Cycle it morning and evening rather than idling the generator. Runtime and fuel come from the calculator after you enter the plate, not from a gallons-per-day guess.

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