How many solar panels do you need to run a well pump?

By the SmartSolarSizer team · Published 20 October 2026

How much electricity does a 1 HP pump use?

About 1.2 kWh for every hour it runs. Franklin Electric's application manual lists 1,210 W at full load for a standard 1 HP, 4-inch submersible motor at 230 V (Franklin Electric). The horsepower on the plate is the motor's output: 1 HP is 746 W of shaft power, and losses mean the motor draws about 1.6 times that from the supply. Use the full-load watts, never HP × 746.

Hours are the other half, and a well pump runs far less than people expect. It only switches on to refill the pressure tank, so its daily run time is simply your water use divided by its flow:

The US EPA says the average American family uses more than 300 gallons of water a day at home (EPA WaterSense). A pump delivering 10 gallons a minute moves that in half an hour. Your flow depends on the pump and the depth, so check its pump curve, or time how long it takes to refill the tank from cut-in to cut-out. Livestock, a garden or an orchard can multiply the total.

A deep well doesn't change the method. Depth decides which motor you need and how fast it can push water up, so a deeper well usually means more watts, more minutes, or both. Once you know the motor's full-load watts and its daily run time, the rest is arithmetic.

Source: Franklin Electric AIM Manual, 2026, 60 Hz. Start-up surge is locked-rotor amps × 230 V, rounded, so treat it as an upper estimate.

How to calculate solar panels for a water pump

1. Running watts: the full-load watts from the motor plate or manual. If it only lists amps, volts × amps gives an upper estimate.
2. Daily energy: watts × hours a day ÷ 1,000 = kWh.
3. Panels: kWh ÷ what one panel makes on a day where you live. Off grid, use your darkest month, not the yearly average.
4. Inverter: continuous rating at least 1.25 × running watts, and a surge rating that covers the start-up watts.

Run a 1 HP pump through that and it's almost anticlimactic. 1,210 W for half an hour is 0.6 kWh. A 430 W panel in New York makes 1.66 kWh on an average day and 1.21 kWh even in December, so one panel does it. Double the pumping to an hour and you need 1–2 panels there. A ½ HP pump (0.3 kWh for 30 minutes) and a 1.5 HP pump (0.9 kWh) both fit on a single panel on an average day in all 14 locations below, though the 1.5 HP pump needs 2 in a northern December; with 545–585 W "solar plates", as sold in Pakistan and India, there's even more margin.

Start-up surge: the part that trips inverters

An induction motor pulls its locked-rotor current until it's up to speed, usually for less than a second. For a 1 HP 2-wire pump that's 48.7 amps, about 11,200 W at 230 V and roughly 9 times its running power. An inverter that can't deliver it shuts down, and the pump never starts. Franklin's own minimum generator size for that motor is 6 kW, for a pump that runs on 1,210 W.

The wiring matters more than most buyers realise. A 3-wire pump has a separate control box with a start capacitor at the surface, and in Franklin's figures it starts on 14–29% less current than the 2-wire version of the same size; its minimum generator drops to 4 kW. If you're replacing a pump anyway, 3-wire is the solar-friendly choice. Better still is a soft-start or constant-pressure drive that ramps the motor up. Grundfos describes its SQE system as having "low starting current and smooth, steady acceleration" (Grundfos).

How much inverter do I need for a 1 HP water pump?

On this page's rule, 2,000 W continuous with a surge rating of at least 9,600 W for a 3-wire pump, or 11,200 W for a 2-wire one. The continuous figure is easy; the surge is what rules out most small inverters. Our main calculator is more cautious and sizes the continuous rating from the surge (surge × 1.25), so for the same 1 HP pump it will suggest 12,000–14,000 W unless you fit a soft starter.

When you compare inverters, check how long the surge rating lasts as well as its size; low-frequency, transformer-based units generally handle motor starts better than small high-frequency ones. Most US submersibles run on 230–240 V, so you'll need a 240 V or split-phase output. And the battery has to deliver that surge too, so check its maximum discharge current, not just its kWh.

Pressure tank size and how often the pump starts

Every start is a surge on the inverter and a stress on the motor. A bigger pressure tank means fewer, longer runs. Franklin limits single-phase motors to 300 starts a day up to ¾ HP and 100 a day from 1 HP, and wants at least one minute of running per start. A tank that's too small, or has lost its air charge, makes the pump short-cycle. On a solar system that's the first thing we'd fix, before buying a bigger inverter.

2, 3 and 5 HP submersible pumps for farms

Irrigation pumps in Pakistan and India are a different scale: they run for hours, not minutes, so energy matters as much as surge. We won't guess wattages for these motors because they vary by make and voltage. Read the full-load kW (or volts and amps) from the plate, and remember a plate showing output in kW, such as HP × 0.746, understates what the motor draws. Then scale with the table, which shows the panels for every 1 kW of motor input running 6 hours a day.

Multiply by your motor's kW and round up. In Lahore, for example, plan on 1.68 kW of panels for every kW of motor if you need full pumping through the July monsoon. Large pumps like these are usually best run solar-direct in daylight, through a pump drive that soft-starts the motor and slows it as the sun fades, with water stored in a tank or sent straight to the field. Storing a full day's pumping would take about 7.4 kWh of battery for every kW of motor. If the motor is three-phase, the inverter or drive needs a three-phase output.

Store water, not electricity: solar-direct DC pumps

For a cabin, a homestead or a stock tank, a solar-direct pump is often the neatest answer. It runs from the panels whenever the sun is up and fills a cistern or storage tank, and you draw water from the tank at night. No battery, no big inverter. Grundfos's SQFlex, for example, can run on DC straight from panels or on AC (Grundfos). It pumps less on cloudy days, so size the tank to carry you through a few of them.

Battery for pumping at night

Because the energy is small, so is the battery. Thirty minutes of a 1 HP pump is 0.6 kWh, and allowing for usable capacity and losses, 0.6 ÷ 0.81 = 0.7 kWh of lithium battery. A ½ HP pump needs 0.4 kWh for the same half-hour. The surge, not the capacity, decides whether the battery and inverter pair will cope.

Common questions

Sources

Solar output for every location comes from the European Commission's PVGIS 5.3 (1 kW system, panels at the best fixed angle facing the equator, 14% system losses), retrieved 20 October 2026. Panel counts assume 430 W panels, the most common size in 2025 home solar quotes (EnergySage).

• Franklin Electric AIM Manual, 2026, 60 Hz submersible systems
• EPA WaterSense: how we use water
• Grundfos SQE constant-pressure system
• Grundfos: SQFlex solar water pumping

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