Free tool No. 1
How long to run your pool pump
Long enough to move the whole pool through the filter once a day. For a 20,000-gallon pool on a 1.5 HP variable-speed pump, that’s 3.7 hours at full speed, or 8.5 hours at 1,500 RPM for about 81% less electricity. Slower and longer is cheaper.
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Worked example
A 20,000-gallon pool, a 1.5 HP variable-speed pump (2,000 W at full speed) and a hot week.
- 1
Flow at full speed
1.5 HP pump ≈ 90 gpm at 3,450 RPM
- 2
Slow it to 1,500 RPM
Flow scales with speed: 90 gpm × 1,500 ÷ 3,450 = 39 gpm
- 3
Hours for one turnover
20,000 gal ÷ 39 gpm ÷ 60 = 8.5 h
- 4
Hot week (90 °F)
8.5 h × 1.25 = 10.7 h
- 5
Power drops with the cube of speed
2,000 W × (1,500 ÷ 3,450)³ = 164 W
- 6
Energy and cost
164 W × 10.7 h = 1.76 kWh × $0.17/kWh = $0.30 a day
Run at 1,500 RPM for 10.7 hours a day: about $8.97 a month, against $46.92 at full speed.
The speed-cubed rule is an ideal estimate: real pumps save a little less because of the plumbing. Use your pump's label for the most accurate numbers.
Hours and cost at each speed
| Speed | Flow | Hours a day | kWh a day | Cost a month |
|---|---|---|---|---|
| 3,450 RPM | 90 gpm | 3.7 | 7.4 | $37.74 |
| 2,800 RPM | 73 gpm | 4.6 | 4.92 | $25.08 |
| 2,400 RPM | 63 gpm | 5.3 | 3.57 | $18.20 |
| 2,000 RPM | 52 gpm | 6.4 | 2.49 | $12.72 |
| 1,800 RPM | 47 gpm | 7.1 | 2.02 | $10.29 |
| 1,500 RPM | 39 gpm | 8.5 | 1.4 | $7.13 |
Very low speeds may not run a heater, salt cell or suction cleaner; check their minimum flow.
Full-speed flow by pump size
| Pump size | Typical flow |
|---|---|
| 0.75 HP | 55 gpm |
| 1 HP | 65 gpm |
| 1.5 HP | 90 gpm |
| 2 HP | 110 gpm |
| 2.5 HP | 130 gpm |
| 3 HP | 150 gpm |
How to set your pump schedule
- 1
Know your volume
Use the pool volume calculator if you're not sure. Everything else follows from it.
- 2
Find your flow and power
The pump label lists horsepower, and often watts or amps. Watts are amps × volts.
- 3
Pick the slowest speed that still works
Your heater, salt cell and cleaner each need a minimum flow. Start there, not at full speed.
- 4
Run long enough for one turnover
Set the timer for the hours the planner gives. Add time in hot weeks, after heavy swimming or after rain.
- 5
Watch the water
If chlorine drops faster than usual or the water dulls, add an hour a day. Run the pump in daylight when you add chlorine.
How we calculate
One turnover means pumping a volume of water equal to the pool: hours = volume ÷ flow ÷ 60. Flow falls in step with pump speed, and power falls with the cube of speed (the pump affinity laws), which is why slow and long uses less electricity than fast and short.
In hot weather we lengthen the run the same way the app does: no change at 60 °F (16 °C) and below, rising evenly to 25% more at 85 °F (29 °C) and above. This planner shares the app’s pump model, so the hours match.
Questions
Do I need to run my pool pump 24 hours a day?
No. Most pools need one turnover a day, which is usually 6 to 12 hours depending on speed. Running longer helps in heat waves, after heavy use or while clearing algae.
Is it cheaper to run a pump on low speed for longer?
Yes. Power falls with the cube of speed, so half speed uses about an eighth of the power for twice the time. In the example on this page, 1,500 RPM uses 81% less electricity than full speed for the same turnover.
Should I run the pump during the day or at night?
During the day if you can, especially after adding chlorine, because that's when sunlight uses it up and circulation matters most. If your electricity is cheaper overnight, split the run between the two.
What if I have a single-speed pump?
Choose Single speed in the planner to get the hours for one turnover. To compare, switch to Variable speed: the planner shows what the same turnover would cost at slower speeds, at your rate.