A standby generator for a well water pump must handle the pump motor starting surge on every cycle throughout the outage, not just the running load. A standard 0.5 HP submersible well pump draws approximately 1,000 running watts and a 2,000 to 3,000-watt starting surge. A 1 HP pump draws approximately 2,000 running watts and a 4,000 to 6,000-watt starting surge. Any Generac Guardian from 14kW upward provides sufficient surge capacity for these pump sizes while powering essential household loads simultaneously.
Why Well Water Backup Is Critical
Homes on well water lose all water service the moment the well pump loses power. No running water means no toilet flushing, no cooking water, no dishwashing, no bathing, and no fire suppression from outdoor hose bibs. Unlike homes on municipal water that continue to receive pressure from the utility system during a local outage, well water homes are completely dependent on the pump motor running continuously. A power outage lasting more than a few hours creates genuine hardship and sanitation concerns for families on well water systems.
Sizing the Generator for Your Well Pump
Identify your well pump horsepower rating from the pump nameplate or the original installation documentation. Common residential well pump sizes: 0.33 HP (requires 750 running watts, 1,500 to 2,250-watt surge), 0.5 HP (1,000 running watts, 2,000 to 3,000-watt surge), 0.75 HP (1,500 running watts, 3,000 to 4,500-watt surge), 1 HP (2,000 running watts, 4,000 to 6,000-watt surge). Add these figures to the running wattage of your other essential loads (furnace, refrigerator, lighting, outlets) to calculate the total simultaneous load the generator must handle.
The Starting Surge Problem
The starting surge is the critical figure. A well pump starting simultaneously with an AC compressor creates a combined surge that can reach 15,000 to 20,000 watts for 1 to 3 seconds. A properly sized generator handles these simultaneous surge events without tripping its main breaker. Generators with insufficient surge capacity for the simultaneous motor start scenario will trip at the worst possible moment, such as when the pressure tank drops to minimum during a hot summer outage and the pump and AC compressor both start at the same instant.
Recommended Generator for Well Water Homes
For well water homes with a standard 0.5 HP to 1 HP pump and central AC, a Generac 22kW Generator with a 200-amp whole-house ATS is the recommended configuration. It handles the AC compressor and well pump starting simultaneously with ample surge capacity to spare. For homes with only the well pump and essential circuits (no AC), a 14kW model with a load-managed transfer switch provides coverage at a lower cost. Browse our Generac home standby generator lineup or call (800) 674-9019 for a free load calculation. Free Freight Insurance Included.