Quick answer: start with 2,700 W of solar
Irrigation is the easiest pump to put on solar because it can run while the sun shines. At 1,500 W for 4 hours it uses 6,000 Wh a day, roughly a 2,700 W array, and if it waters only in daylight, most of that can go straight from the array to the pump with little battery.
Planning result
At 200 W per module, the array target is 14 panels. That count assumes four peak-sun-hours, 75% end-to-end solar yield, 90% conversion efficiency, and a 20% planning margin. Irrigation demand peaks in the long, sunny days of summer, so the load and solar output line up well; spring and autumn need much less.
How an irrigation pump actually uses power
Planning case: a 1 HP self-priming centrifugal sprinkler pump drawing about 1,500 W while it runs, for 4 hours a day in the growing season. Red Lion and Goulds list 1 HP sprinkler pumps at 14 to 16 A at 115 V (7 to 8 A at 230 V).
An irrigation pump runs continuously at close to full power for each watering zone, unlike a household pressure pump that cycles. Daily energy is set by the water applied and the pressure the sprinklers or drip lines need; high-pressure sprinklers take far more power than low-pressure drip for the same water.
Load calculation from running watts and duty cycle
The appliance-class estimate is 1,500 W running for 4 h/day at a 100% duty cycle, an average of about 1,500 W across those hours:
Then losses and reserve raise the energy the system must collect to about 8,000 Wh/day.
Typical manufacturer nameplate/manual range for the irrigation pump class, triangulated with Red Lion (Franklin Electric): Sprinkler pump and Goulds Water Technology (Xylem): GT Irri-Gator self-priming centrifugal pumps instruction manual, then reduced to a conservative planning midpoint; this is not a product specification. Verify the exact unit's nameplate and manual before sizing.
Time each zone and measure the pump with a plug-in energy meter (120 V) or a circuit monitor (240 V); daily kWh is runtime times watts.
Solar and battery sizing table
| Design item | Planning value | Basis |
|---|---|---|
| Appliance energy | 6,000 Wh/day | Running W × hours × duty cycle |
| Solar collection target | 2,700 W | 4 peak-sun-hours, 75% yield, 20% margin |
| 200 W panel count | 14 | Rounded up; real modules must satisfy controller voltage/current limits |
| One-day battery allowance | 10,000 Wh | 90% conversion efficiency, 80% LiFePO4 usable fraction, 20% margin |
| 12.8 V LiFePO4 equivalent | 785 Ah | Nominal planning conversion |
| 25.6 V LiFePO4 equivalent | 395 Ah | Nominal planning conversion |
If watering can wait for daylight, the battery only covers the motor start and passing clouds. Solar-direct DC pumps and pump drives that run from the array without a battery are common for exactly this reason.
Build the closest passing wiring-diagram preset
The Irrigation Pump Planning System preset is an engine-passing starting point whose array, battery bank, continuous inverter rating, and surge rating each meet or exceed this page's stated planning allowances. Adjust it only from measured load data and verified equipment limits.
Inverter and startup current
Use at least 1,900 W continuous with 5,000 W surge for this planning case. Each start draws a motor surge of several times the running watts, and a controller that switches zones by stopping and restarting the pump repeats it; that is what the 5,000 W surge allowance covers.
The 4,500 W startup estimate is not a substitute for the manual's locked-rotor, compressor-start, or motor-start requirements, and an inverter's surge rating usually lasts seconds, not minutes. A battery-to-inverter cable that is too long or too small can pull the DC input below the inverter's low-voltage threshold during that start even when the battery has plenty of energy, so use the diagram machine's real run length.
The common mistake
Ways to cut the load
- Convert sprinklers to drip where possible; lower pressure and flow cut the pump's power.
- Water in the morning while the array is producing.
- Gravity-feed from a raised tank that the pump fills during the sunny part of the day.
- Fix leaks and set pressure regulators so each zone needs fewer minutes.
What to verify before buying equipment
- The exact running watts, startup current, voltage, frequency, and required circuit from the appliance label and manual.
- Actual watt-hours over a representative day; seasonal heating or cooling loads need a design-day measurement.
- Local peak-sun-hours for the worst operating season, plus shade and array orientation.
- Controller maximum input voltage at the coldest expected temperature and maximum output current.
- Battery discharge current, series/parallel permission, terminal torque, low-temperature controls, and overcurrent protection.
- Conductor ampacity, voltage drop, terminal temperature ratings, disconnecting means, grounding, local amendments, and inspection requirements.
For a whole-system load list, use the load and appliance calculator. For the system context around this appliance, continue to the Solar water and well-pump guide.
Frequently asked questions
How much solar do I need for an irrigation pump?
For the planning case on this page (a 1 HP sprinkler pump watering for four hours a day), allow about 2,700 watts of solar at four peak-sun-hours per day. That covers an estimated 6,000 Wh daily load plus conversion, temperature, and recharge margin. Daylight-only watering lets the array supply the pump directly, so the battery can be much smaller.
What size inverter should I use for an irrigation pump?
Plan on at least 1,900 W continuous and 5,000 W surge. The motor start is the peak to plan for; a soft-start pump or a variable-frequency drive reduces it.
What battery size keeps an irrigation pump running for one day?
The one-day planning allowance is about 10,000 Wh nominal usable design capacity, roughly 785 Ah at 12.8 V or 395 Ah at 25.6 V for LiFePO4. Most solar irrigation systems water in daylight and keep the battery small.