How to use the pool pump calculator
- Enter the pool volume. If you don’t know it, work it out with the pool volume calculator.
- Choose a turnover time: 8 hours is a good target for most home pools, 6 hours for heavily used pools.
- If you know your pump’s real flow rate, enter it to check how long one turnover takes.
- Enter the pump’s power draw, daily run time and your electricity price to see the cost.
The formulas
Flow needed (GPM) = Pool gallons ÷ (Turnover hours × 60) Turnover time (h) = Pool gallons ÷ Pump GPM ÷ 60 Energy (kWh/day) = Pump watts × Hours per day ÷ 1,000 Cost per day = kWh per day × Price per kWh
Worked example
A 20,000 gallon pool with an 8-hour turnover:
- Flow needed = 20,000 ÷ 480 = 41.7 GPM
- A pump moving 50 GPM turns the pool over in 20,000 ÷ 50 ÷ 60 = 6.7 hours
- A 1,500 W pump run 8 hours uses 12 kWh a day — $1.80 a day or $54 a month at $0.15 per kWh
Flow needed by pool size
| Pool volume | 6 h turnover | 8 h turnover | 10 h turnover |
|---|---|---|---|
| 10,000 gal (38 m³) | 27.8 GPM | 20.8 GPM | 16.7 GPM |
| 15,000 gal (57 m³) | 41.7 GPM | 31.3 GPM | 25.0 GPM |
| 20,000 gal (76 m³) | 55.6 GPM | 41.7 GPM | 33.3 GPM |
| 25,000 gal (95 m³) | 69.4 GPM | 52.1 GPM | 41.7 GPM |
| 30,000 gal (114 m³) | 83.3 GPM | 62.5 GPM | 50.0 GPM |
Single-speed vs variable-speed pumps
A single-speed pump always runs flat out, so the only way to save money is to run it fewer hours. A variable-speed pump can run slowly most of the day and speed up only for vacuuming, a spa or a water feature. Because power drops roughly with the cube of speed, running at half speed for twice as long moves the same water for about a quarter of the energy. The U.S. Department of Energy notes that a variable-speed pump can save hundreds of dollars a year compared with a single-speed pump, and US federal efficiency standards that took effect in July 2021 effectively require variable-speed motors on many new in-ground pool pumps.
Tips to keep flow up
- Clean the skimmer and pump baskets weekly — clogged baskets cut flow sharply.
- Backwash or clean the filter when the pressure gauge reads 8–10 psi above its clean reading.
- Check your filter’s maximum flow — the pump should never push more than the filter is rated for.
- Run the pump during off-peak hours if your utility has time-of-use rates.