Pool Pump Electricity Cost

A pool pump is usually the second or third biggest electricity user in a house that has one. A single-speed 1.5 HP pump on 8 hours a day costs around $54 a month at the current US average of $0.16/kWh, and comfortably past $100 on a California tariff. That is the gap variable-speed pumps are sold into, and unusually for an efficiency upgrade, the sales pitch is basically true.

Power calculation

kW = horsepower x 0.7457 / (motor_efficiency / 100)

kWh per day = kW x run_hours

Monthly cost = kWh per day x 30 x electricity_rate

A 1.5 HP motor at 80% efficiency draws 1.5 × 0.7457 / 0.80 = 1.40 kW. Run 8 hours a day at $0.16/kWh that is $53.69 a month, or $644 a year.

Why variable-speed pumps win, and it is not marketing

The affinity laws say pump power scales with the cube of speed. Halve the speed and you use one eighth of the power (0.5³ = 0.125), while still moving half the water. Run the pump twice as long at half speed and you filter the same volume for a quarter of the energy.

That is the whole trick, and it is why the savings are so large. A variable-speed pump running slow for most of the day, with a short burst at high speed for vacuuming or the heater, typically lands 50 to 80% below a single-speed pump doing the same job. This calculator assumes 70%, in the middle of that band.

Variable-speed units also use permanent-magnet motors that are more efficient at any given speed, so some of the gain arrives before you touch the schedule at all. California’s Title 20 has required variable-speed capability on residential pool pumps for years, with the threshold tightening over successive updates, and several other states have followed.

On the price premium

A variable-speed pump costs meaningfully more up front than a single-speed one, and how much more depends on brand, horsepower and who fits it, so this page will not guess at your local price. Instead the result works out what each $100 of premium takes to recover. Multiply by whatever your actual quote is above the single-speed alternative and you have your own payback period, rather than someone else’s.