Pool Covers

What Size Heat Pump Do I Need for My Pool?

Once you know the correct pool heat pump size required for your pool, you can confidently buy a unit that ensures you have the perfect temperature to enjoy swimming all year round.

There are factors to consider in determining the right pool heater size, including:

  •  Length and breadth – meaning the surface area of your pool
  • The particular climatic conditions in your location (air temperature, wind, evaporative cooling, etc.)
  • How often you use your pool
  • Your pool cover

You can use an online swimming pool heat pump size calculator that takes into account pool dimensions as well as location, heat loss rate, average depth and so on.

Pool Heat Pump Sizing

How to calculate pool heat pump sizes

Correct heat pump pool heater sizing ensures that you maintain the comfortable temperature you want, and for most people, the ideal temperature is more or less 29C.

The main problem with heating a pool is heat loss, not water volume. Pool water loses heat via evaporative cooling that naturally occurs due to solar radiation. It is the job of the heat pump to replenish heat when cooling occurs.

Thus, the rate of heat loss of your pool should also be considered when choosing the right pool heat pump size.

To calculate estimated heat loss for a 6 m x 9 m pool with a water temperature of 24C and air temperature of 18C:

  •         Subtract 24 – 18 =  6
  •         Multiply difference 6 x 6 m x 9 m = 324
  •         Multiply 324 with the constant 0.027 = 8.75

Thus, the heat loss rate for this pool is 8.75 kW.

For round-shaped pools (including oval-shaped pools), use the radius in calculating the surface area. With the use of a pool heat pump size calculator, multiply the radius (r) by itself and with the constant pi (3.14).

That is R x R x 3.14. For a rounded pool with a radius of 4.6 m under the same temperature conditions, the surface area is 4.6 x 4.6 x 3.14 = 66.44 m2.

Then multiply 66.44 x 6 x 0.027. The heat loss rate for this particular pool is 10.76.

Pool Heat Pump Size

How many BTUs do I need for a 38,000-litre pool?

Another way to determine the right pool heater size without using a swimming pool heat pump calculator is by basing it on the pool’s volume.

This is an easier method of estimating because you only need to look at a heat pump sizing chart available online. Some charts even specify the BTUs required for a particular swim season.

Here is a chart based on volume:

Pool water volume


Spring & Fall


37,584 litres

14.65 kW

14.65 kW

24.91 kW

75,708 litres

24.91 kW

24.91 kW

32.24 kW

94,635 litres

24.91 kW

32.24 kW

36.63 kW

*Sizing based on in-ground pools

Your heat pump should be able to heat your pool by at least 0.11 degrees per hour. In other words, pool heaters should be able to increase water temperature by at least 0.560C per hour on an 862-litre of volume. That is the minimum requirement.

Is a bigger pool heat pump better?

Heat pumps have kW ratings between 14.65 kW to 43.96 kW. Smaller pools can get away with a 14.65 kW heat pump. For a larger pool, you might need a unit that heats water faster.

If your pool heater cannot replace heat lost through evaporative cooling, it can be undersized and needs replacement.

Also, do not worry about oversizing. The larger the output is, the faster your unit can heat water.

Generally speaking, it is important to oversize the heat pump as possible. Doing so means warming your pool fast while minimising energy costs.

Is it cheaper to heat a pool with gas or heat pump?

Which pool equipment is better – a gas heater or a heat pump? It depends on your requirements. But in terms of the operating costs, heat pumps are the better option.

The running cost of heat pumps is lower because they generally use less energy over long periods than gas heaters.

Another advantage of heat pumps is they last a longer time. Because of the high heat produced within the unit and its movable parts, a gas heater requires frequent repairs and fails before most heat pumps will.

Under careful maintenance, a pool heat pump can last up to 10 years or more. Keep your pool equipment free of debris, such as pine needles and leaves.

Also, ensure that rodents are kept at bay. Turn your heater off when it is not in use.

How can Pool Covers & Rollers help?

We’re experts in Pool Heating solutions. Based on the size of your pool. we can let you know exactly what pool heat pump will fit your needs without blowing your budget.

Simply call us on 0477241953 today.

Our Madimack Heat Pumps

Elite V3 – Heat Pump Series

Re-engineered from the ground up to deliver the most advanced residential pool heater in the Australian market. Fitted with the latest inverter technology, the Elite V3 offers the highest efficiency levels, smallest installation requirements and quietest operational levels available.

Economic Heat Pump Series

Our Eco range of units are highly energy efficient pool heating systems, perfect for homeowners who are focused on minimising their utility bills.

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Original price was: $18.70.Current price is: $16.40. sqm
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