In short: a typical residential well pump — 20 GPM against 150 ft of head, running 6 hours a day — costs about $0.87 a day, or roughly $26 a month, at $0.15/kWh. Smaller sump and circulator pumps that run only occasionally cost far less; large irrigation or booster pumps running for hours cost more. Enter your own numbers above for an exact figure.
These figures are planning aids based on typical efficiency ranges and electricity rates. For a load calculation feeding an electrical panel or a purchase decision, confirm with a licensed electrician or engineer.
How to calculate pump energy cost
Running a pump costs money because its motor draws electricity the whole time it operates. To find that cost, you first need the pump's electrical input power — how many kilowatts it actually pulls from the wall — then multiply by how long it runs and what you pay per kilowatt-hour.
Worked example. A well pump moves 20 GPM against 150 ft of head. Water horsepower = 20 × 150 × 1 ÷ 3960 = 0.76 WHP. At 65% pump efficiency, brake horsepower = 0.76 ÷ 0.65 = 1.17 BHP. At 90% motor efficiency, electrical input = 1.17 × 0.746 ÷ 0.90 ≈ 0.97 kW. Running 6 hours a day, that pump uses 0.97 × 6 = 5.79 kWh a day, which costs 5.79 × $0.15 ≈ $0.87 a day — about $26.44 across an average 30.4-day month.
Nameplate HP is not the same as electrical draw. A motor labeled "1 HP" delivers 0.746 kW of mechanical output at full load, but it draws more than that from the wall because the motor itself is not 100% efficient. That is why the calculator asks for pump and motor efficiency separately when you size from flow and head — see the Pump Power Calculator for water- and brake-horsepower alone.
Why pump and motor efficiency change the answer
No pump converts all of its input energy into moving water — some is lost to friction, turbulence and internal recirculation inside the pump casing, and more is lost as heat in the motor's windings. Small single-stage centrifugal pumps typically run 40–70% efficient; well-matched, correctly sized pumps sit toward the top of that range, while an oversized or worn pump can fall well below it. Standard-efficiency motors run 80–90% efficient, while premium (NEMA-rated) motors reach 90–95%.
Because these two losses multiply together, a pump-and-motor combination at 45% × 85% delivers a combined efficiency of about 38% — meaning you buy nearly two and a half times the electricity that the water horsepower alone would suggest. Upgrading either efficiency figure lowers the electric bill for the same amount of water delivered; see the Variable-Speed Pump Savings Calculator for how a variable-speed drive can cut that further by matching pump speed to actual demand.
Reference: motor size and running cost
Approximate electrical draw and running cost by common motor size, assuming the entered horsepower equals electrical input (1 HP = 0.746 kW), 8 hours of daily runtime, 365 days a year, at $0.15/kWh. Use the "Enter motor power directly" mode above for your own numbers.
| Motor size | Input power | Daily energy | Annual cost |
|---|---|---|---|
| 1/2 HP | 0.37 kW | 3.0 kWh | $163 |
| 1 HP | 0.75 kW | 6.0 kWh | $327 |
| 1.5 HP | 1.12 kW | 8.9 kWh | $490 |
| 2 HP | 1.49 kW | 11.9 kWh | $653 |
| 3 HP | 2.24 kW | 17.9 kWh | $980 |
| 5 HP | 3.73 kW | 29.8 kWh | $1,633 |
Worked examples
Home well pump
$26.44/mo
20 GPM against 150 ft of head, at 65% pump and 90% motor efficiency, running 6 hours a day at $0.15/kWh — about $0.87 a day.
1/2 HP sump pump, seasonal
$20.41/yr
Running roughly 1 hour a day through a wet season, entered directly as 0.5 HP at $0.15/kWh — a small but steady add to the annual bill.
3 HP irrigation pump
$17.50/mo
Entered directly as 3 HP, running 4 hours a day on 3 watering days a week — costs add up fastest for pumps with both high power and long runtimes.
What else affects the result
Duty cycle vs. continuous runtime. Sump and sprinkler pumps cycle on and off with demand, so their true daily runtime is often far shorter than it feels — track actual pump-on time with a timer if you can, rather than guessing.
Demand charges and time-of-use rates. Some utilities bill commercial or larger residential accounts extra for peak demand, or charge more per kWh at certain hours. This calculator uses a single flat rate; if your bill has tiered or time-of-use pricing, run the calculation separately for each rate period.
Startup surges. Motors draw a brief inrush current — often several times the running current — when they start. For pumps that cycle on and off frequently, this has a small but real effect on the bill that a simple running-power calculation does not capture.
Frequently asked questions
How much does it cost to run a well pump?
For a typical 20 GPM well pump lifting water 150 feet, expect around $0.87 a day, or about $26 a month, assuming 6 hours of daily runtime, 65% pump efficiency, 90% motor efficiency and $0.15 per kWh. Deeper wells, higher flow rates, or a less efficient pump raise the cost — use the calculator above with your own numbers.
How do I find my pump's power draw without a wattmeter?
Check the motor's nameplate for its rated kilowatts or horsepower and switch the calculator to "Enter motor power directly." The tool converts horsepower using 1 HP = 0.746 kW. For an exact figure, a clamp meter reading amps, multiplied by voltage, gives the true electrical draw.
Does pump efficiency really change my electric bill?
Yes. A pump that is only 45% efficient uses roughly 45% more electricity than one that is 65% efficient to move the same water, because more of the input energy is lost as heat and turbulence instead of doing useful work. Motor efficiency losses stack on top of that.
How much does a sump pump cost to run?
Sump pumps run intermittently, so cost depends heavily on rainfall. A 1/2 HP sump pump running about 1 hour a day, most days of the year, costs roughly $20 a year at $0.15 per kWh — far less than a well or irrigation pump that runs for hours at a stretch.
Why does head, not just flow, affect the running cost?
Pumping power depends on both how much water moves and how far it must be lifted or pushed against pressure. Doubling the head roughly doubles the power needed for the same flow, so a deep well or a pump feeding a multi-story building costs more to run than a shallow, low-pressure system moving the same gallons per minute.
Sources & references
- Hydraulic Institute. Standards for Centrifugal, Rotodynamic Pumps (ANSI/HI 1.1–1.5).
- U.S. Department of Energy, Office of Energy Efficiency & Renewable Energy. Pumping Systems guidance.
- National Electrical Manufacturers Association (NEMA). MG-1 Motors and Generators.
John Mac, PE
Water Systems Specialist · Austin, Texas
Texas-licensed Professional Engineer with 13+ years in residential water systems and 180+ completed projects. Writes and reviews the calculators on watercalculator.us. Read full bio
Texas PE (2016) · BS Civil Engineering, Hydraulics (2013)