Estimate what a pool pump could cost to run at a reduced speed using the pump affinity laws (a theoretical estimate), or compare your own measured power readings and hours — then download or email your estimate.
Theoretical saving: 2,190 kWh (75%) less electricity a year — about $766.50 a year incl GST — under these theoretical assumptions.
Theoretical — affinity-law estimate, not measured performance
At 50% speed
Flow
208 L/minvs 416 L/min at full speed
Electrical input
125 Wvs 1,000 W · 87.5% less power
Head
25% of referencespeed squared
Hours per day
16 hvs 8 h at full speed
Daily water volume
199,680 Lvs 199,680 L at full speed
Energy per day
2.00 kWhvs 8.00 kWh · 75% less daily energy
Power vs energy: power draw is 87.5% lower (speed cubed), but daily energy also depends on hours — 16 h at 125 W gives 75% less daily energy.
Theoretical annual running costs
Theoretical saving: 2,190 kWh (75%) less electricity a year — about $766.50 a year incl GST — under these theoretical assumptions.
Full speed (reference)$1,022.00/yr2,920 kWh a year
50% speed (theoretical)$255.50/yr730 kWh a year
Saving a year$766.50$63.88 a month on average · 75% less energy
Payback: No payback shown — enter a total installed upgrade cost to see one.
NZ dollars incl GST at $0.35 per kWh for 365 operating days a year. Electricity only — daily fixed charges are not included. Hypothetical, not a guaranteed saving or payback.
How the affinity laws are applied
Speed ratio r = 50% = 0.5
Flow = 416 L/min × r = 208 L/min
Head = r² = 25% of the full-speed head
Input power = 1,000 W × r³ = 125 W
Hours = 8 h ÷ r (same estimated daily volume) = 16 h
kWh per day = watts ÷ 1000 × hours; annual cost = days × kWh per day × rate
Assumptions behind this estimate
Theoretical affinity-law estimate: flow scales with speed, head with speed squared and power with speed cubed, assuming the same impeller and constant efficiency.
416 L/min is Aqua Clear's nominal example for IT24-416; 1,000 W is the manual's rated IT24 input. These are not a verified coincident installed operating point. Replace them with full-speed site readings where available.
The speed percentage is a theoretical rotational-speed ratio, not a promise that a controller's capacity percentage equals that speed or power.
Static head, pipe resistance, motor/drive efficiency and minimum equipment flow change the actual result. Matching estimated daily volume does not prove equivalent filtration, skimming or sanitisation.
More about installed performance
The affinity laws compare equivalent operating points at constant fluid density and pump efficiency. Static head, pipe resistance and changing motor / drive efficiency mean actual electrical power and installed flow can differ from the theoretical scaling.
The 10–100% speed range is a mathematical ratio for this estimate. It is not a controller setting or a permitted operating range — check the controller's minimum speed and the flow actually delivered on site.
Matching the estimated daily volume does not prove equivalent filtration, skimming or sanitisation, or that a heater or chlorinator receives its minimum flow.
This is not a measurement of installed performance and not a guaranteed saving or payback. Use "Enter power readings" with measured watts for a site-specific comparison.
This is a schedule scenario, not proof the pool will be filtered as well. On site, confirm:
Confirm the actual flow at the installed system head (pipework, filter, heater and valves) — not the pump's maximum-flow rating.
Confirm the daily turnover the pool needs is still achieved at the proposed speed and hours.
Confirm surface skimming still works at the lower flow.
Confirm the salt chlorinator and any heater still receive their minimum flow (flow switches) during their operating hours.
Confirm the pump primes reliably and allow any manufacturer priming period.
Allow boost periods for vacuuming, cleaners, water features, backwashing or heavy bather load.
Considering a variable-speed pump? Aqua Clear sells the iGarden InverterFlow range. This calculator doesn’t pick or size a pump — ask Aqua Clear about a suitable pump and schedule for your pool. Browse iGarden InverterFlow pumps
Your estimate
Download a branded PDF of this comparison, or email it to yourself. It records the method (affinity-law estimate), every input and its assumptions, and is an indicative estimate — not a quote or a guaranteed saving.
Theoretical and indicative estimates only — not measured installed performance; savings and payback are not guaranteed. Confirm filtration on site before changing a pump’s speed or runtime.
