Heat pump calculator

What sits behind the numbers

• Climate — Bureau of Meteorology monthly normals, 1991–2020, read off the station table for each location: Perth Metro 009225, Bunbury 009965, Geraldton Airport 008051, Albany Airport 009741, Kalgoorlie-Boulder 012038, Karratha Aero 004083. Wind is the mean of the 9 am and 3 pm readings. Solar exposure is not on those tables — those figures are published regional monthly means, and the month-to-month shape is estimated rather than sourced.
• Heat loss — evaporation (the dominant term, and the one wind drives), convection, radiation to the night sky and a small conduction allowance, less absorbed solar gain. Day and night are modelled separately rather than averaged. The Bureau measures wind at 10 m over open ground, so it is stepped down to what the water surface feels behind a fence; the exposure setting does the rest.
• Blanket — evaporation all but stopped, convection and radiation roughly halved, and about a third of the sun reaching the water. Over a full year that comes out around a 65% cut in heating energy, which is where published figures for pool covers sit. It assumes the cover actually goes on for the hours you set, every day.
• Heat pump — Sensaheat quote nameplate capacity at 27 °C air / 27 °C water / 80% humidity, so that is the 100% point; output falls to about 68% at 15 °C air. COP is modelled across the lift from air to water, which is why a warmer target costs more per kWh, and it is scaled to reproduce Sensaheat's own published figure of about 9 at their rating point on a half-speed compressor.
• Sizing — the hardest month inside your chosen season, taken at a cool, dull spell rather than that month's average, plus a 5% margin so the unit is not running flat out to hold temperature. Running costs and the month-by-month table use the true averages, so they read as a normal year.
• Heat-up — from the pool's own temperature at the start of your season, running the unit continuously, which is how a pool is actually brought up from cold. Day to day it then only needs the hours shown in the table.
• Circulation pump — the heater only transfers heat while water is moving, so the pump is part of the running cost. Only the hours beyond the filtration you would run anyway are charged to heating; the baseline hours happen whether the pool is heated or not. On an older single-speed pump those extra hours can cost as much as the heater itself, which is the strongest argument for a variable-speed pump alongside a heater.
• What is estimated — the climate normals and the heat pump rating conditions are sourced. The cool-spell allowance, the wind step-down, the blanket factors and the part-load efficiency gain are engineering assumptions, chosen to be conservative but not measured on your pool. Treat the result as a starting point for a conversation, not a specification.

Indicative only. Real pools have shade, spa spillovers, water features and leaks. Confirm the final selection with your AGent rep before ordering, and check the electrical supply at the equipment pad — the larger units are three phase.