Irrigation Energy Cost Calculator
Calculate pumping energy cost from Total Dynamic Head, flow rate, pump and motor efficiency, and electricity or diesel prices.
About this calculator
This calculator translates the physical work of pumping irrigation water into a dollar figure, using the standard hydraulic-power chain engineers use to size and budget pump stations. It first builds Total Dynamic Head (TDH) — the total resistance the pump has to overcome — by summing static lift (vertical distance to the water source), friction loss in the pipe, and operating pressure converted from PSI to feet of head using the 2.31 ft-per-PSI relationship. Water horsepower, the theoretical power needed to move that flow against that head with no losses, comes from the classic WHP = (GPM × TDH) / 3960 formula. Dividing by pump efficiency gives brake horsepower — the actual shaft power the pump needs — and dividing that by motor efficiency and converting with the standard 0.7457 kW-per-horsepower factor gives the electrical demand in kilowatts.
From there the calculator branches on fuel type: electric cost is kW × electricity rate, while diesel cost applies a typical fuel-consumption factor of 0.044 gallons per horsepower-hour to brake horsepower, then multiplies by diesel price. Costs are also expressed per acre-inch and per 1,000 gallons, which is the real basis for comparing pumping plants or deciding whether upgrading pump or motor efficiency pays for itself. The main assumption is that TDH and efficiency stay constant across the whole run — in reality, static lift can change as a well drawdowns or a reservoir level drops over a season, and pump efficiency varies with flow rate on its actual performance curve, so treat this as a representative operating-point estimate rather than a full-season energy audit.
Inputs
Results
Total Dynamic Head (ft)
279
Cost per hour ($)
$6.34
Cost per acre-inch ($)
$3.59
How to Use This Calculator
- Enter Flow rate (GPM), Static lift (ft), and Friction loss (ft).
- Set Operating pressure (PSI), Pump efficiency (%), and Motor efficiency (%).
- Adjust Electric rate ($/kWh), Diesel price ($/gal) as needed.
- Review Total Dynamic Head (ft), Cost per hour ($) ($), and Cost per acre-inch ($) ($).
- Use Water horsepower (WHP) and Brake horsepower (BHP) to inform your decision.
How the result changes with Static lift (ft)
| Static lift (ft) | Total Dynamic Head (ft) | Cost per hour ($) | Cost per acre-inch ($) |
|---|---|---|---|
| 75 | 204 | $4.64 | $2.62 |
| 113 | 242 | $5.50 | $3.11 |
| 225 | 354 | $8.05 | $4.55 |
| 375 | 504 | $11.46 | $6.48 |
What each input means
- Flow rate (GPM)
- Pump discharge flow rate in gallons per minute.
- Static lift (ft)
- Vertical distance from water source to discharge point.
- Friction loss (ft)
- Head loss due to pipe friction (from friction loss tables).
- Operating pressure (PSI)
- Required system operating pressure at the pivot or nozzles.
- Pump efficiency (%)
- Pump efficiency from performance curve (typically 65-80%).
- Motor efficiency (%)
- Electric motor efficiency (typically 88-95%).
- Electric rate ($/kWh)
- Cost per kilowatt-hour of electricity.
- Diesel price ($/gal)
- Cost per gallon of diesel fuel.
- Operating hours/season
- Total pump operating hours per irrigation season.
- Fuel type (0=Electric, 1=Diesel)
- Select power source: 0 for electric, 1 for diesel.
What each result means
- Total Dynamic Head (ft)
- Total head the pump must overcome (lift + friction + pressure).
- Water horsepower (WHP)
- Theoretical power to move water (before efficiency losses).
- Brake horsepower (BHP)
- Actual power required at the pump shaft.
- Power demand (kW)
- Electrical power demand including motor efficiency.
- Overall plant efficiency (%)
- Combined pump and motor efficiency.
- Cost per hour ($)
- Energy cost per hour of pumping.
- Cost per acre-inch ($)
- Energy cost to pump one acre-inch of water.
- Cost per 1,000 gal ($)
- Energy cost per 1,000 gallons pumped.
- Seasonal energy cost ($)
- Total energy cost for the irrigation season.
- Seasonal energy (kWh)
- Total electricity consumed per season.
- Seasonal diesel (gal)
- Total diesel fuel consumed per season.
- Capacity (acre-in/hr)
- Water delivery capacity in acre-inches per hour.
How this is calculated
Worked example, using the default values
- Identify Input Parameters4 parametersFlow rate (GPM) = 800, Static lift (ft) = 150, Friction loss (ft) = 25, Operating pressure (PSI) = 45 = 10 input(s) provided
- Calculate Total Dynamic HeadTotal Dynamic Head = staticLiftFt + frictionLossFt + pressureFt279 = 279
- Calculate Cost per hour6.34 = $6.34
- Calculate Cost per acre-inch3.59 = $3.59
- Calculate Water horsepowerWater horsepower = (flowRateGpm * tdh) / 396056.4 = 56.4
- Calculate Brake horsepowerBrake horsepower = whp / pumpEff78.3 = 78.3
Engine last updated . Checked against 2 independently-derived tests — how we verify calculators. Built by Paul Gunder, a software engineer, not a licensed financial, medical, or legal professional.
Frequently Asked Questions
What's the difference between water horsepower and brake horsepower?
Water horsepower (WHP = GPM × TDH / 3960) is the theoretical power needed to move your flow rate against the total head with zero losses — an idealized minimum. Brake horsepower divides WHP by pump efficiency, giving the actual power the pump shaft has to deliver to overcome real mechanical and hydraulic losses inside the pump. Brake horsepower is always higher than water horsepower because no real pump is 100% efficient.
How does the calculator decide whether to show electric or diesel costs?
It checks the fuel type input: 0 selects electric, computed as kilowatts (brake horsepower × 0.7457 ÷ motor efficiency) times your electric rate, while 1 selects diesel, computed by applying a typical fuel-consumption factor of 0.044 gallons per horsepower-hour to brake horsepower and multiplying by diesel price. Only the selected fuel type's cost feeds into cost per hour and the seasonal totals — the calculator doesn't blend the two.
Why does operating pressure get converted to feet of head?
Total Dynamic Head needs every component expressed in the same unit, and pump curves and horsepower formulas are conventionally built around feet of head rather than PSI. The calculator converts using the fixed relationship of 2.31 feet of head per PSI, then adds that to static lift and friction loss to get TDH — the single number that drives every downstream horsepower and cost calculation.
Why might my actual pumping cost per hour differ from this calculation?
The model assumes TDH and efficiency stay constant for the whole run, but real conditions drift: static lift can increase as a well drawdowns during the season or a reservoir level drops, and pump efficiency isn't fixed — it varies with flow rate along the pump's actual performance curve. Treat this as a representative operating-point estimate for a single set of conditions, not a full-season energy audit that tracks how those conditions change over time.
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