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How to size a Pool Heat Pump?

How to choose a Pool Heat Pump size for your swimming pool: everything you need to know to install or upgrade your pool heat pump

selecting the optimal pool heat pump size:

Choosing the right size pool heat pump is crucial for keeping your water comfortably warm without breaking the bank. Achieving the perfect pool temperature requires a carefully chosen heat pump.

Here's a general guide on how to size a pool heat pump. By following these guidelines and consulting with a pool professional, you can choose the right heat pump for your needs and enjoy the benefits of a warm and inviting pool year-round:

  • COP rating
  • Calculate your pool volume
  • Desired temperature
  • Professional guidance

COP: COP, which stands for Coefficient of Performance, is a crucial metric used to measure the efficiency of a pool heat pump, it resembles a ratio between the input energy (electricity) and output energy (Heat/ Cool). It essentially tells you how well the heat pump converts electrical energy into useful heat (or cooling, depending on its mode). 

The higher the COP rating, the better the efficiency: Generally, a higher COP indicates a more efficient heat pump. This means it uses less electricity to provide the same amount of heating or cooling, resulting in lower operating costs and reduced environmental impact. 

Here are some additional points to remember:

    • A COP of 1 would mean the heat pump is simply converting electricity into heat with no additional efficiency gain, and a heat pump with COP 2 means that for every 1 kW of Electricity the heater is generating 2 kW of heat
    • Most modern heat pumps have COPs ranging from 3 to 7, with some advanced models reaching even higher values. For example, the InverECO Heat Pump has a COP range of 10.8~6.2 making it more energy-efficient. Another excellent option is InverELITE V3 boasting a COP range spanning from 16.4~7.Madimack Pool Heating
    • When comparing different heat pumps, please pay attention to their COP ratings at your typical operating conditions to make an informed decision.

The efficiency (COP) of a heat pump is influenced by the ambient air temperature and humidity, as it extracts heat directly from the surrounding air.  

Here's an example of COP chart taken directly from our testing facility of InverELITE 11 KW pool heat pumpScreen Shot 2019-01-13 at 8.38.31 pm-1

In this example, a COP of 5 means that for every 1 kilowatt (kW) of electricity used, the heat pump delivers 5 kW of heat to the pool.

We hope this explanation clarifies what COP means in the context of deciding the size of pool heat pumps. Feel free to ask if you have any further questions!

Top tip: Running a large heat pump at half capacity might be more efficient than a small one at full capacity due to better performance at partial loads. But, it depends. The right size for your needs is crucial for optimal efficiency. Choose wisely!

Best pool heating options in Australia.


Calculate your pool volume to determine the right heat pump size: We'd be happy to help you calculate your pool volume to determine the right heat pump size! However, we'll need some information from you first:

    • Pool Shape: Knowing the shape (rectangular, oval, kidney-shaped, etc.) will guide us in using the appropriate formula.
    • Dimensions: Provide the length, width, and depth of your pool in feet or meters.
    • Average Depth (Optional): If your pool has varying depths, an average depth measurement will suffice for an estimation.
    • Water features: Such as infinity edges, waterfalls, jets, or any other special feature inside the pool should be considered before  choosing the right size, please let us know if any.

Once we have this information, we can calculate your pool volume and guide you toward selecting the suitable pool heat pump size. Here are some common pool shapes and their volume formulas:

Rectangular Pool: Volume = Length x Width x Depth

Oval Pool: Volume = (Length x Width x Depth) x 0.55

Circular Pool: Volume = (π x Radius² x Depth)

Kidney-Shaped Pool: Divide the pool into sections (rectangular, triangular, etc.) and calculate the volume of each section separately. Then, add the volumes of all sections for the total pool volume.

Consult a pool professional for an accurate assessment is always recommended, especially for complex pool shapes or unique environmental factors.


Consider your desired temperature increase: The desired temperature is a crucial factor when choosing the right pool heat pump. Here's how it plays a role:

  • Calculate the difference between your desired swimming temperature and the average air temperature during your coldest usage month. This represents the "temperature increase" your heat pump needs to achieve.
  • Heating speed: An undersized heat pump will struggle to maintain your desired temperature, while an oversized one will be inefficient and costly. Aim for a heat pump that can raise the temperature by 0.20-0.25°C per hour.

What temperature should I set for my pool heat pump?

  • Wind, pool covers, and the surrounding environment: These factors contribute to heat loss, so you might need a slightly larger heat pump to compensate.
  • Climate: Colder climates might require a more powerful heat pump.


Seek Professional Guidance: 

  • Consulting a qualified pool professional is highly recommended. They can provide tailored advice based on your specific pool dimensions, climate, and usage patterns.
  • Experts can account for additional factors like pool covers, solar panels, and insulation, which significantly impact heat pump requirements.


  • An undersized heat pump will struggle to maintain your desired temperature, and will be inefficient and costly to operate. Choose one that fits your needs and budget.
  • Investing in the appropriate size heat pump ensures optimal performance, energy efficiency, and a comfortable swimming experience. 


Madimack's lead engineer - Westley Collins says, "InverElite V3 pool heat pump has been a revolutionary product that delivers better airflow, higher efficiency, quieter operation and performance". 


Trade partners refer to installing Madimack pool heat pumps as the most energy-efficient and durable way to heat your pool. 

Find a local dealer/installer in your local area on Madimack's Dealer Finder online.

Engaging a specialist to support you through Madimack Pool Heating
the process can optimise your heating solution further

Enviro Friendly: All round best pool heat pumps for Australia

Madimack spoke with pool owners who have installed the Madimack pool heat pump - InverELITE V3, they noted that it's a great and solid product that comes with smooth installation with everlasting flawless operation. Madimack Pool Heat Pumps are a Awards Winner for 2023.

Read more Madimack pool heat pump reviews on


Use Madimack’s pool heater sizing calculator to generate a personalised report on the best pool heating options for you:

Pool Heat Pump Calculator

Fill in the details below and a detailed pool heating evaluation will be emailed instantly.
Note: You can use this calculator as many times as you need for different pool volumes if you are unsure.

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