For this registered outage plan—a 1 HP, 230 V, 3-wire submersible well pump with two LED bulbs scheduled at the peak—we calculate a running-capacity planning target of 1,550 W. If the two phone chargers also run, the ordinary simultaneous load is 1,270 W.
Neither figure is a complete generator size. The pump's AC starting requirement is unknown, so we cannot confirm whether a particular portable, standby or inverter generator can start it. Motor startup is the decisive constraint.
Before choosing a generator, verify the pump or control-box starting requirement and compare the total demand during startup with the generator's model-specific surge capability. The generator must also provide an output and connection arrangement compatible with this 230 V pump.
Loads and capacity in this outage plan
The registered schedule models these direct AC loads:
| Load condition | Demand |
|---|---|
| Pump and two LED bulbs at the scheduled peak | 1,240 W |
| Every enabled AC load, including phone charging | 1,270 W |
| Running-capacity planning target for the scheduled peak | 1,550 W |
| AC starting estimate | unknown |
At the scheduled peak, the modeled loads are 1 HP 230 V 3-wire submersible example 1,210 W, LED light bulb ×2 30 W. The planning target applies this scenario's declared headroom policy to the 1,240 W scheduled on-power envelope. It is not a universal sizing rule, and it does not include the missing motor-start demand. If your actual simultaneous load differs, update the load plan rather than reusing this target unchanged.
The schedule also estimates 1.21 kWh of energy use. Watts measure power needed at a moment; kilowatt-hours measure energy used over time. This energy estimate does not predict fuel consumption or generator runtime.
The missing pump-start requirement is the deciding constraint
A well-pump motor can require more power while starting than after it reaches normal speed. In this case, the pump's starting watts, locked-rotor current or equivalent manufacturer startup requirement was not supplied. The calculation therefore leaves the AC starting estimate as unknown.
The engine records 1,240 W as already operating at the modeled start time, but reports no motor start adds watts. That wording means no startup increment was available to add. It must not be read as evidence that the pump has no starting surge.
No candidate generator running or surge rating was selected either. Consequently, the tool returns an unknown fit rather than a pass or fail. A generator can meet the ordinary running target and still be unable to start the pump or maintain acceptable output during startup.
The bound information also includes conditional 4 kW minimum guidance, but only for a matching Franklin 1 HP, 230 V, 3-wire motor and control, an externally regulated generator, and the pump operating alone. The example pump has not been verified as that matching system, and the guidance does not cover all the listed household loads. Treat it as model-conditional guidance to investigate, not as a confirmed recommendation for this setup.
Check your pump and generator before choosing a size
- Find the pump and control information. Look for a label on accessible pump-control equipment, the control box, installation records or pump documentation. Do not open energized equipment or enter a well enclosure to find a label.
- Record the exact configuration. Note horsepower, rated voltage, phase, whether the pump is 2-wire or 3-wire, and the motor and control-box model numbers. Matching the motor and control information matters for this 3-wire example.
- Find model-matched starting data. Look for starting watts, locked-rotor current or manufacturer generator guidance for that motor-and-control combination. Keep this value unknown if matching information is unavailable; do not substitute a generic motor multiplier.
- Check the proposed generator ratings. Compare its continuous rating with the full simultaneous running load. For startup, account for the verified pump-start requirement plus any other loads that may already be operating, then compare that total with the generator's applicable surge capability. Also check how long that surge capability is available.
- Confirm voltage and connection compatibility. This example requires a source compatible with a 230 V pump. Verify the generator's output configuration, receptacle or hardwired connection, breaker arrangement and compatibility with the pump controls. Wattage alone does not establish compatibility.
- Account for automatic restarts. A pressure switch can call for the pump when system pressure falls. Include lights, chargers and any other loads that could still be operating when that happens.
Have a qualified electrician evaluate permanent, transfer-equipment or electrical-panel connections. This calculation is not a wiring design.
Essential and optional loads
In this plan, the well pump is the critical water-supply load. The LED bulbs and phone chargers are secondary loads.
Start with the essential load: establish the pump's startup requirement and evaluate whether a candidate generator can operate the pump by itself. This isolates the most important and least certain event.
Then add coincident loads: include the lights, chargers and other household loads that must operate at the same time. The complete enabled load set reaches 1,270 W before any pump-start increment is added.
Removing or scheduling phone charging can lower ordinary coincident demand. Turning off lights can lower it further. Neither change supplies the missing pump-start value, and scheduling cannot guarantee that an automatically controlled pump will not restart while another load is on.
Limits of this planning estimate
This is a declared simulation, not a measurement of your pump or proof of generator compatibility. Its schedule estimates 2.42 kWh over 48 h, but it does not calculate fuel use or guaranteed runtime.
The reported unserved energy is none only because the modeled source has no selected running or surge capacity limit. It does not mean that a real generator passed the capacity check.
The calculation does not validate surge duration, voltage regulation, waveform, frequency response, grounding or neutral arrangements, breakers, transfer equipment, wiring, receptacles or pump-control compatibility. Its one-motor-start assumption also does not prove that coincident starts or pressure-switch restarts will be served.
For a pump with different horsepower, voltage, phase or wiring, do not scale this 1 HP result by assumption. Use model-matched pump data and create a separate calculation. No supported result for another configuration is calculated on this page.
Next step: verify the nameplate and startup data
Write down the pump and control-box model numbers, horsepower, voltage, phase and wiring type. Then obtain matching startup guidance and enter that value with the continuous and surge ratings of the generator you are considering.
If a rating is unavailable, keep it marked unknown rather than treating it as zero. For a different horsepower or voltage, review the supplied well-pump data or create a separate editable load plan using the links below.