The formula
kWh per day = watts × hours ÷ 1,000
Cost = kWh × price per kWh
If you only know volts and amps from the motor label, watts ≈ volts × amps × 0.9. The 0.9 allows for the motor’s power factor, so the result is a slight overestimate of real power for many motors.A 1.5 horsepower single-speed pump typically draws about 1,500 to 2,000 watts. The most reliable number is a reading from a plug-in or clamp energy meter, or your pump’s spec sheet.
Worked example
A 1,800 W single-speed pump, 8 hours a day, 210 days a year, 18.4¢ per kWh
- Energy = 1,800 × 8 ÷ 1,000 = 14.4 kWh a day
- Cost = 14.4 × $0.184 = $2.65 a day, $81 a month, $556 a year
Why variable speed saves so much
Pumps follow the affinity laws: flow rises in step with motor speed, but power rises with the cube of speed. ENERGY STAR puts it simply: reducing pump speed by half lets the pump use one-eighth as much energy. To move the same amount of water at half speed you run twice as long, so the daily energy is one-quarter:
Power at speed s = full power × s³
Energy for the same water = full-speed energy × s²
The same pump job at 50% speed
- Power = 1,800 × 0.5³ = 225 W
- Run time = 8 ÷ 0.5 = 16 hours to move the same water
- Energy = 3.6 kWh a day, so $139 a year instead of $556, saving $417
Yearly cost to move the same water at different speeds
Show the numbers
| Speed (%) | Hours a day | Cost a year |
|---|---|---|
| 30 | 26.7 | $50 |
| 40 | 20 | $89 |
| 50 | 16 | $139 |
| 60 | 13.3 | $200 |
| 70 | 11.4 | $273 |
| 80 | 10 | $356 |
| 90 | 8.9 | $451 |
| 100 | 8 | $556 |
The model assumes the pump’s efficiency stays the same at every speed. In practice, motors and impellers lose some efficiency at very low speeds, and some jobs need full speed: suction cleaners, water features, spa jets and heaters with a minimum flow. Most owners run low speed for filtering and a short high-speed block for those.
Other ways to cut pump costs
- Run it only as long as you need. One turnover a day is a common baseline. The pump size calculator shows how long that takes.
- Use off-peak hours if your utility has time-of-use rates.
- Keep the filter clean. A clogged filter raises resistance, so the pump moves less water for the same power.
- Check for rebates. Many utilities offer rebates for variable-speed or ENERGY STAR certified pumps.
Frequently asked questions
How much does it cost to run a pool pump per month?
A typical 1,800 W single-speed pump running 8 hours a day costs about $81 a month at 18.4¢ per kWh. Use your own wattage, hours and rate for an exact figure.
How much does a variable-speed pool pump save?
Running at half speed for twice as long uses about a quarter of the energy. In the example that’s $417 a year. ENERGY STAR notes that halving speed cuts power to one-eighth.
How many watts does a pool pump use?
A 1 to 1.5 hp single-speed pump commonly draws around 1,000 to 2,000 W. Variable-speed pumps may draw only a few hundred watts at low speed.
Is it cheaper to run a pool pump at night?
Only if your utility charges less at night. Energy use is the same, but time-of-use rates can make off-peak hours much cheaper.
How long should I run my pool pump?
Long enough for at least one full turnover a day, plus extra time when chlorinating with a salt cell or heating.
Why is my variable-speed pump not saving as much as expected?
Usually because it spends long periods at high speed for a cleaner, heater or water feature. Try shortening those blocks and filtering at the lowest speed that keeps the water clear.
Sources
- ENERGY STAR Certified Pool Pumps. U.S. EPA, ENERGY STAR.
- U.S. residential electricity rates, June 2026 (EIA Electric Power Monthly). ElectricRates.org summary of EIA data.
- The critical role of circulation and turnover in residential pool performance. Pool Magazine.
Reviewed November 7, 2026. We check the formulas against the sources above and re-run the worked examples whenever we update this page. Found something wrong? Tell us.