Pool Pump Running Cost Calculator
The pump is usually the second-largest electrical load in a house with a pool, behind air conditioning. This works out what your current schedule costs, and what the same turnover would cost run long and slow.
Picking one fills in a typical wattage and run time.
A clamp meter on the supply gives the real number. The preset is typical for a 1.5 HP class pump.
Check your bill. The US residential average was about $0.18/kWh in the first half of 2026.
Power falls much faster than pump speed, while flow only falls in step with it. That is the whole argument for variable speed. The textbook says half the RPM takes an eighth of the power; real pumps land nearer a sixth, so running twice as long costs about a third as much for the same turnover.
Result
Enter your pump details
The fields start on ordinary values so you can see what each one wants. Nothing is worked out until you put your own numbers in.
The pump is usually the second-largest electrical load in a house with a pool, behind air conditioning. This works out what your current schedule costs, and what the same turnover would cost run long and slow.
Getting an accurate answer
- Pump power falls much faster than speed. The textbook says halving the RPM cuts power to an eighth while flow only halves, and real pumps land nearer a sixth. Either way, running slow for twice as long is far cheaper for the same turnover.
- If you do not know your pump wattage, a clamp meter on the supply is the accurate answer. Failing that, the horsepower estimate below is close enough to make the decision.
- Check your utility for a pool pump rebate before you buy. The four I checked in September 2026 paid $300 to $900, and all four required an ENERGY STAR certified pump.
What it actually costs, worked through
A 1.5 HP single-speed pump draws around 1,900 watts in practice. Run eight hours a day at $0.17 per kWh, a little under the 2026 US average of about 18 cents, that is 15.2 kWh a day — $2.58 daily, $78 a month, roughly $390 over a five-month season.
Run the same pool on a variable-speed pump at 1,750 RPM, about half speed, and it draws around 320 watts. Moving the same water takes about 15.8 hours, and costs about $26 a month.
Those are the two numbers the whole decision rests on, and the gap is not a rounding difference. Over the roughly seven years DOE expects a pump to last, it comes to more than the pump costs.
The cube law, and where real pumps fall short
This is the piece of physics that makes variable speed worth the money, and it is worth understanding rather than taking on faith.
Flow scales with speed. In the textbook, power scales with the cube of speed. Halve the RPM and you get half the flow, but only an eighth of the power draw.
Turnover is a volume, so half the flow simply means running twice as long. Two times an eighth is a quarter: the same water moved, for 25% of the energy. That is the textbook figure. Real pumps fall short of it, and the example above, 320 watts at 1,750 RPM against a single-speed pump's 1,900, comes out at about a third.
In ENERGY STAR's test data, moving water at the low test point took about a fifth of the energy per gallon that full speed did, where the arithmetic predicts a seventh. A motor and its drive lose some efficiency as they slow down. DOE's national estimate, which also counts the better motor a variable-speed pump carries, came to 71% less than single speed.
The effect is steep and it runs both ways. At 80% speed real pumps come close to the textbook, and they still use about 66% of full speed's energy for equal turnover, against the textbook's 64%. Most of the saving lives in the last part of the slowdown, which is why a variable-speed pump left on a high default captures almost none of it — and why the most common way to waste one is to install it and never program it.
Why the horsepower on the label will not tell you
People reach for nameplate horsepower to estimate draw, and it does not work.
1.5 HP is 1,119 watts of shaft output. The pump draws around 1,900 to produce it — the difference is motor and hydraulic efficiency, about 59% overall on a single-speed pool pump. So the label understates consumption by a third, and that is before service factor, which is its own trap: a "1 HP" motor with a 1.65 service factor is doing more work than a "1.5 HP" with 1.0.
A clamp meter on the supply is the honest answer and costs about $30. Failing that, the wattage estimates in this calculator are close enough to make the decision, because the decision is not close.
Compare pumps on total horsepower and flow at your head rather than on the number printed largest on the box.
Payback, without the optimism
On the example above, variable speed saves about $260 a season. Mid-range pumps were about $1,600 in September 2026, which takes roughly six of those five-month seasons to pay back. Where the pool runs all year, the saving is about $630 and the same pump pays back in about two and a half years.
Check for a utility rebate before you buy. The four I checked in September 2026 paid $300 to $900, all of them for ENERGY STAR certified pumps. A $1,600 pump with a $350 rebate is back in about five of those seasons.
Two things push payback the wrong way and are worth being honest about: a short season, and cheap electricity. A pool open three months in a region paying $0.11 is a much weaker case than a year-round pool paying $0.30, and the calculator above uses your own numbers rather than mine for exactly that reason.
The other half of the return is not on the bill. A pump run slow is quieter, easier on its own bearings and seal, and gentler on the plumbing — which is worth something even in the months when the arithmetic is marginal.
Questions about this calculator
How much does it cost to run a pool pump?
A 1.5 HP single-speed pump drawing around 1,900 watts for 8 hours a day costs about $2.58 a day at $0.17/kWh — roughly $78 a month, or $390 over a five-month season. The same turnover on a variable-speed pump at 1,750 RPM costs nearer $26 a month, about a third as much.
Are variable-speed pool pumps worth the money?
For most pools open more than a few months a year, yes. DOE's national analysis put the running cost 71% below single speed. On the example above that saves around $260 over a five-month season, which pays back a $1,600 pump in about six seasons, or about two and a half years on a pool open all year. Rebates I checked in September 2026 ran $300 to $900 on ENERGY STAR certified pumps.
How many hours a day should I run my pool pump?
Long enough for one full turnover of the water, which on a variable-speed pump at low RPM usually means 8–12 hours. Slow and long filters better than fast and short, sanitizes more evenly, and costs a fraction as much.
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