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Solar Irrigation Pump Calculator

Enter your crop, irrigated area, pump head, and location — get daily water requirement, flow rate, pump HP, solar array size, and annual savings vs diesel.

Units:
Field and crop details
acres
ft
Solar irrigation system for 10 acres
114 × 400W panels · 27.4 HP pump
Daily water requirement543,080 gal/day
Pump flow rate needed1131.4 GPM
Pump power required27.37 HP (20.41 kW)
Daily pumping energy163.3 kWh/day
Solar array size45.35 kW (114 panels)
Storage tank (2 cloudy days)1,086,160 gal
Est. system cost$147,006
Annual diesel pump cost (comparison)$27,551/yr
Payback vs diesel5.3 yrs
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How to Use This Calculator

Select crop type, area, and irrigation method

Start with your crop type — this determines daily water requirement per acre. Vegetables need the most (about 2 inches/day); wheat the least (about 1 inch/day). Enter your irrigated area in acres or hectares using the toggle at the top. Irrigation method is critical: drip at 90% efficiency means the pump only needs to deliver 11% more water than the crop needs; flood at 60% efficiency means the pump delivers 67% more than the crop needs — a dramatically larger system.

Enter total dynamic head and pump type

Total dynamic head (TDH) is the total pressure the pump must overcome — it includes the vertical lift (static head) plus friction losses in the pipes. For a well pump, TDH = depth to water + pressure head needed at the field. Enter this in feet or meters. Submersible pumps are used in wells; surface pumps work for rivers, ponds, and tanks at shallower depth.

Read the results

The output shows daily water volume, required flow rate (GPM or LPM), pump horsepower, solar array size, panel count, storage tank recommendation for cloudy days, system cost, and payback compared to running a diesel pump for the same load.

The Formula

Daily Field Water = Area (acres) × Water Req (in/day) × 27,154 gal/acre-inch Pump Volume = Field Water ÷ Irrigation Efficiency Flow Rate (GPM) = Pump Volume ÷ (8 hrs × 60 min/hr) Pump Power (kW) = Flow (GPM) × Head (ft) ÷ (3960 × Pump Efficiency × 1.341) Daily Pump Energy = Pump kW × 8 hrs Solar Array (kW) = Daily kWh ÷ (PSH × 0.75 system efficiency) Panel Count = Ceiling(Solar kW × 1000 ÷ 400W) Storage Tank = Pump Volume × 2 days Annual Diesel Savings = Daily kWh × 120 days × ($4.50/gal ÷ 3.2 kWh/gal)

The 3960 constant converts GPM and feet to hydraulic horsepower. Pump efficiency of 70% reflects typical centrifugal pump performance; submersible pumps in good condition often achieve 75-80%. The 0.75 solar system efficiency accounts for wiring losses, inverter efficiency, soiling, and temperature derating. Annual diesel comparison assumes 120 irrigation days per year at $4.50/gallon and 3.2 kWh per gallon of diesel.

Example

Sam's 10-Acre Corn Field — Kansas City, MO

Sam irrigates 10 acres of corn using a sprinkler system drawing from a river. Total dynamic head is 50 ft. The location gets 4.8 peak sun hours. He currently pays $4.50/gallon for diesel to run a generator-driven pump.

CropCorn, 1.5 in/day water requirement
Area10 acres
IrrigationSprinkler (75% efficiency)
Head50 ft total dynamic head

Result

Daily water volume~543,000 gal/day (gross pump volume)
Flow rate~1,130 GPM
Pump power~20 HP (15 kW)
Solar array~34 kW (85 panels)
Storage tank~1.1M gal (2 cloudy days)
System cost~$108,000
Annual diesel savings~$25,000/yr
Payback~4.3 years

A 10-acre corn operation running sprinklers from a river needs a substantial 34 kW solar array, but the payback is just 4.3 years against diesel costs. After payback, Sam saves $25,000/year — and eliminates fuel price volatility and generator maintenance entirely. Many agricultural states also offer additional solar incentives for farm-based solar systems.

FAQ

For 1 acre of vegetables irrigated with drip (90% efficiency) at 2 inches/day water requirement with a 30 ft head, you need approximately 0.5-1 HP pump and 1-2 kW solar array (3-5 panels). The key variables are head and irrigation efficiency — switching from drip to flood irrigation for the same acre roughly doubles the pump power needed. At the small end (garden scale under 0.5 acres), a 0.5 HP solar direct pump with a 400-600W panel is often sufficient.
Total dynamic head (TDH) is the total pressure a pump must overcome and equals: (1) Static lift — vertical distance from water surface to the pump discharge (for wells: depth to water table); (2) Friction head — pressure losses in pipes and fittings, typically 10-20% of static lift for well-designed systems; (3) Pressure head — operating pressure needed at sprinkler heads or drip emitters (typically 10-30 psi = 23-69 ft). For a well with a 40 ft water table and a sprinkler system needing 30 psi (69 ft), TDH ≈ 40 + 10 (friction) + 69 = 119 ft. Your pump supplier can calculate TDH precisely from your site.
It depends on whether your irrigation timing flexibility. Solar direct pumps (no batteries) pump only when the sun shines — typically 6-10 hours per day. They are 20-30% cheaper since there are no batteries to buy or replace. They work well when you have a storage tank to hold daytime-pumped water for use at any time. Battery-backed systems allow pumping any time, including early morning and evening — better for residential well systems or when specific timing matters. For agricultural irrigation with a field or tank buffer, solar direct is usually the economical choice.
Solar saves roughly $1.20-1.50 per kWh compared to diesel generator-powered pumps (diesel at $4.50/gal, 3.2 kWh/gal efficiency). A 10 kW pump running 8 hours per day for 120 irrigation days uses 9,600 kWh/year — saving $11,500-14,400/yr vs diesel. For a 50-acre operation with a 75 kW pump system, savings reach $85,000-100,000 per year. Payback periods of 3-6 years are typical for agricultural solar pumping replacing diesel, after which operating costs drop to near zero for 20+ years.
Multiple programs stack for agricultural solar: (1) USDA REAP grant (Rural Energy for America Program) — covers up to 50% of solar system cost for farms and rural businesses, with additional loan guarantees up to 75% of remaining cost. (2) Federal ITC at 30% applies to farm solar systems as a business investment tax credit. (3) Bonus depreciation / Section 179 — farm equipment including solar can often be fully expensed in year one. (4) State agricultural solar incentives — many states have additional grants specifically for irrigation efficiency and on-farm renewable energy. Combined, these incentives can reduce effective system cost by 60-80%.

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