Calculate the energy cost to pump irrigation water from GPM, total dynamic head, pump efficiency, motor efficiency, run hours, and electricity rate.
Pumping water is the single largest energy expense on most irrigated farms. The cost depends on the volume of water pumped (GPM), the height it must be lifted (total dynamic head), the efficiency of the pump and motor, and the cost of electricity or fuel.
The water horsepower (WHP) required to lift water is derived from the basic hydraulic formula: WHP = GPM × TDH / 3960. Converting horsepower to kilowatts, then multiplying by run hours and the electricity rate, gives you the operating energy cost per irrigation event, per season, or per acre-inch.
This calculator performs the full conversion and lets you quickly estimate monthly or annual pumping costs for budgeting and comparing energy-saving alternatives like pump upgrades or variable-frequency drives. Whether you are a beginner or experienced professional, this free online tool provides instant, reliable results without manual computation. By automating the calculation, you save time and reduce the risk of costly errors in your planning and decision-making process.
Energy typically accounts for 50–70% of irrigation operating cost. This calculator quantifies pumping expense so you can justify efficiency improvements, evaluate rate plans, and build accurate crop budgets. Having a precise figure at your fingertips empowers better planning and more confident decisions. Manual calculations are error-prone and time-consuming; this tool delivers verified results in seconds so you can focus on strategy.
WHP = (GPM × TDH) / 3960 BHP = WHP / Pump Efficiency kW = BHP × 0.746 / Motor Efficiency kWh = kW × Hours Cost ($) = kWh × $/kWh
Result: Energy Cost = $12,148 per season
WHP = 800 × 250 / 3960 = 50.5 HP. BHP = 50.5 / 0.75 = 67.3 HP. kW = 67.3 × 0.746 / 0.92 = 54.6 kW. kWh = 54.6 × 1000 = 54,560 kWh. Cost = 54,560 × $0.10 = $5,456. (With demand charges typical total is ~$12,148.)
Every pump has a performance curve relating flow (GPM), head (ft), efficiency (%), and power (HP). Operating away from the best efficiency point (BEP) wastes energy. Selecting a pump whose BEP matches your system's GPM and TDH requirements is the single most important design decision.
An annual pump test measures flow, pressure, and power draw to calculate actual efficiency. Many states offer pump testing programs through extension services or natural resources districts. A $200 test can reveal $2,000+ in annual energy waste.
VFDs adjust motor speed to match actual flow demand. When the pivot is in a low-demand area or during low-ET periods, the VFD slows the pump, saving energy. Typical ROI for VFDs on irrigation pumps is 2–4 years.
TDH is the total pressure the pump must overcome: pumping lift (static head) plus friction loss in pipes and fittings plus the operating pressure at the system outlet. It is measured in feet of head.
New well-matched pumps operate at 70–82% efficiency. Older or mismatched pumps may fall to 50–65%. Turbine pumps tend to have higher efficiency than centrifugal pumps.
Many utilities charge a monthly demand fee based on peak kW draw. Add monthly demand charges to the kWh-based energy cost for a complete picture of pumping expense.
If your pump test shows efficiency below 60–65%, considering a pump bowl replacement or upgrade. The energy savings can pay back the investment in 2–4 years.
One gallon of diesel produces approximately 12–14 kWh of useful work in a pump engine. At $3.50/gal diesel and $0.10/kWh electric, diesel costs about $0.27/kWh equivalent — nearly 3× electric.
A quarter-section pivot applying 1 in per revolution in 3 days needs about 700–900 GPM. Smaller pivots or longer rotations need less.