Optimize your variable speed pump settings. Calculate power consumption and turnover rates at different RPMs to maximize energy efficiency. Fine-tuning your pump speeds allows you to balance proper skimming and filtration with the lowest possible electricity cost.
A variable-speed pump lets you trade flow for big energy savings, and this tool quantifies that trade at each RPM. Enter the pump's rated power and flow at full speed (its nameplate, e.g. 2.7 kW or about 3.5 HP at 3,450 RPM), then the RPM you want to model. Also enter your pool volume and electricity price per kWh so the tool can convert RPM choices into daily turnover and dollars. If you have minimum-flow equipment, note its requirement: salt chlorinators, heaters, and many automatic cleaners need a flow switch to close, often around 1,800-2,400 RPM. The point of the calculator is to find the lowest RPM that still completes one full turnover within your run window while clearing those minimum-flow thresholds. Measure your real volume first, because turnover time, and therefore the cheapest viable speed, depends directly on it.
Method uses the Pump Affinity Laws: flow scales linearly with speed, but power scales with the cube of speed. So flow2 = flow1 x (RPM2 / RPM1), and power2 = power1 x (RPM2 / RPM1)^3. Worked example: a pump drawing 2.7 kW and 80 GPM at 3,450 RPM is dropped to 1,725 RPM (half speed). Flow becomes 80 x 0.5 = 40 GPM (151 LPM), and power becomes 2.7 x (0.5)^3 = 2.7 x 0.125 = 0.34 kW, one-eighth the draw. To turn over a 24,000-gallon pool at 40 GPM takes 24000 / 40 / 60 = 10 hours. Running 10 h at 0.34 kW = 3.4 kWh; at $0.18/kWh that is about $0.61 per day, versus 5 h at 2.7 kW = 13.5 kWh (~$2.43) for the same turnover at full speed, roughly a 75% saving.
The savings are real but only if the slow speed still does the job, so accuracy protects both your water and your equipment. Run too slow and a single daily turnover may not fully skim surface debris or distribute chlorine, letting algae establish in dead spots; the fix is a short daily high-speed 'skim' period plus a long low-speed filtration block. The most common mistakes are setting filtration RPM below a heater or salt cell's flow-switch threshold (the equipment simply won't fire), and forgetting that lower flow can under-feed a chlorinator so free chlorine drifts down, retest FC after changing your schedule. Do not chase the absolute minimum RPM at the expense of clarity. Re-tune speeds seasonally: warmer water and heavy bather loads need more turnover and higher FC, so raise run time or speed in summer and ease off in cooler months.
For standard filtration, most VSD pumps are most efficient at low speeds between 1,000 and 1,500 RPM. This moves enough water for clarity while using very little power.
According to the Pump Affinity Laws, if you cut the speed in half, the power consumption drops to one-eighth. This is why VSD pumps save so much money.
Most saltwater chlorinators and heaters have a minimum flow requirement. You must set your pump speed high enough (usually 1,800+ RPM) to trigger the flow switch.