Why "how many kW?" is the first real question

Almost every pool-heating enquiry starts with a price. It should start with a capacity. Until you know how many kilowatts your pool actually needs, a price is meaningless — the same pool can be quoted with wildly different units, and the cheapest one is often the one that never reaches your target temperature in December.

The good news is that sizing is not guesswork. It is a calculation, and it depends on a small number of inputs you can measure today.

What actually determines the size

  • Surface area, not volume. Most heat leaves through the water surface by evaporation. Two pools of identical volume but different surface areas need different capacities. Any quote based on cubic metres alone has skipped the main variable.
  • Target temperature vs ambient. The bigger the gap you are asking the system to hold, the more power it takes — and that gap is far larger in January than in September.
  • Wind exposure. An open North Coast plot loses far more heat than a sheltered courtyard pool of the same size.
  • Season of use. A summer-only pool and a year-round pool are two different machines. Sizing on summer conditions is the single most common way to end up disappointed in winter.
  • Thermal cover. Covering the surface out of hours cuts evaporation loss dramatically, which directly reduces both the capacity you need and the hours it runs.

Why rules of thumb fail here

"So many kW per cubic metre" is the shortcut most suppliers use, and it is wrong often enough to matter. It ignores surface area, wind, and the season you actually want to swim in. Undersize the unit and it never closes the gap on cold nights — it simply runs continuously replacing losses. Oversize it and you have paid for capital you will never use.

Get the number for your pool in a couple of minutes

Rather than leave you to estimate, we built the calculation into a tool our own engineers use. Enter your pool dimensions, target temperature, exposure and the season you want to swim, and it returns the required capacity in kW — then matches it against real units, including quantity and expected surplus.

Open the pool heating calculator — free, no obligation, and it gives you a defensible number to compare any quote against.

If you would rather we run it for you, book a free site assessment and we will do the load calculation on site.

Which units the calculator sizes against

The tool does not return an abstract number. Once it has your required kW it matches that against the actual ranges we supply, so you can see real options, how many units each solution needs, and how much spare capacity you would be paying for:

  • HeatMaster heat pumps — X20-10P, HeatMaster I, X20-24P, X20-34P, III X20, IV JBR and E4-70, covering everything from a hot tub up to roughly 160 m³ of water.
  • GRAT I-Pro full-inverter residential range — GT030TM-SPI through GT150TH-SPI. We are the authorized exclusive dealer for GRAT heat pumps in Egypt.
  • GRAT commercial inverter range — 65K, 100K, 135K, 195K, 220K (GT500TH-SPO), 250K and 290K, for club, hotel and Olympic-scale pools.
  • Electric heaters — Elecro (9–96 kW), Altra and Vulcan, where fast, simple heating is the priority.
  • Gas heaters and boilers — Heat Flow wall-mounted, Raypak, Hayward and Unical condensing kON.

Seeing the shortlist matters as much as seeing the number: it is what turns "you need about 45 kW" into "this unit, or two of these, with this much surplus."

Then use the number properly

Once you know the required kW, a quote becomes easy to judge. Ask each supplier what capacity they are proposing and why, whether it was sized for winter or summer, and what it costs to run — not just to install. A supplier who cannot answer the first question has not done the calculation.

For the wider picture see our guide to pool heating in Egypt, or what pool heating costs.