What Heat Pump Size Should I Get for My Pool?

Opting for electric heat pumps presents the most efficient method to heat your swimming pool, provided you select the appropriate capacity. Calculating the correct size ensures maximum savings and an extended swimming season.

Determining the correct size for your pool’s heat pump requires a meticulous calculation. Unlike gas pool heaters, heat pumps extract heat from the air to warm your pool water. Several variables need consideration in this calculation, including:

  • The average temperature of your area, including all seasons.
  • Your pool size.
  • The number of months you plan to heat your pool.

Variations in Electric Heat Pumps

Electric heat pumps designed for pools come in two distinct types:

  1. On/off heat pumps deactivate upon reaching the desired temperature and reactivate when the water cools.
  2. The second type is notably more energy-efficient and features an intelligent inverter that adjusts its speed to either slow down or accelerate, maintaining the pool at the preset temperature. Complete inverter heat pumps can autonomously regulate their speed, resulting in lower power consumption than on/off heat pumps. Furthermore, inverter pool heat pumps typically boast a superior Coefficient of Performance (COP), a factor we’ll delve into shortly before the calculations.

Measuring COP and Kilowatts (kW)

The Coefficient of Performance (COP) is a metric indicating the efficiency of a heat pump by comparing the energy it produces to its consumption. A higher COP signifies more effective heat production and lower energy costs.

For example, a pool heat pump with only an on/off function operates either at total capacity or not at all, akin to driving at 100 km/h, abruptly stopping, and then accelerating again. Such heat pumps typically have a COP of around 5, indicating the generation of 5 kW of heat for every 1 kW of energy used.

Electric heat pumps featuring full inverter technology are the most efficient, often boasting a COP exceeding 12. These types of electric heat pumps are recommended above others due to their efficiency, reduced environmental impact, and silent operation.

What Is the Science Behind Pool Heat Pump Sizing?

Given their expertise in navigating the intricate science of achieving maximum efficiency in pool heating, it is reasonable to enlist professional assistance in sizing your heat pump. The process can be complex and pricey if you miscalculate any elements.

Let’s delve into the steps for sizing your heat pump based on your pool size:

Step 1: Find Out Your Pool’s Size

Suppose you need to figure out your pool’s size. In that case, you can calculate the size of your pool by multiplying the length, width, and average depth – for example, a pool measuring 6.5m in length, 2.5m in width, and with an average depth of 1.1m will have a capacity of 17.875 cubic meters or 17,875 litres (L= 6.5 x W=2.5 x D=1.1).

Step 2: Calculate the Required kW for Your Pool Size

Once you know your pool’s capacity, you can match it with an appropriately sized pool heat pump. While some people use the formula m3 ÷ 2500 to determine kW from the heat pump, this method doesn’t consider various factors and is not a dependable guide. Instead, consider this general guideline on pool capacity and heat pump sizes, bearing in mind that heat pump sizes and pool capacities vary by brand:


Pool Size kW Required
20m3 Minimum 9kW
40m3 Minimum 12kW
60m3 Minimum 16kW
80m3 Minimum 16kW


For those residing in cooler regions of Australia, such as Victoria, South Australia, or Tasmania, opting for the higher end of the kW capacity is advisable. Consider going up to the next size for increased heat pump efficiency.

Step 3: Other Factors You Should Keep in Mind

A fundamental rule for pool heat pumps is that smaller pools require smaller heat pumps. If you’re unsure, pick a size bigger and not smaller. While the upfront cost may be somewhat higher, the long-term savings you enjoy in your power bills are substantial.

Other factors can influence your pool heat pump’s efficiency, including:

  • Each unit has a low and high Coefficient of Performance (COP) dependent on ambient temperature and humidity, making efficiency location-dependent. Colder climates may necessitate a larger heat pump.
  • Lack of a pool cover can cause your electric heat pump to work harder to maintain pool warmth, emphasising the importance of using a cover, which can reduce heating costs by up to 80%.
  • Above-ground or huge pools may incur higher costs to maintain temperature.

What You Should Prepare Before Requesting a Quote

Seeking advice from a pool heating specialist is crucial for accurately sizing your heat pump. They will consider every aspect to ensure you achieve your desired outcome – extended pool heating throughout the year with the lowest possible operating costs.

Before you call for a quote, you should have the following information ready:

  • Your pool size (height, width, and depth or capacity in litres).
  • The placement of your pool filter pump in your house.
  • Whether the pool is above ground or located in a highly shaded area.
  • During which months do you wish to swim in your pool?
  • Whether or not you have a pool cover (If you don’t have one, it is strongly recommended to have one!).

The Bottom Line

Choosing the right electric heat pump for your pool involves careful consideration of size, efficiency, and environmental impact. 

The two types of heat pumps, on/off and inverter, highlight the significance of energy-efficient technology. It would help if you calculate the Coefficient of Performance (COP) and kilowatts to determine the most effective heating solution. Sizing your heat pump according to pool dimensions, location, and climate ensures optimal performance. 

Collaborating with a pool heating expert streamlines the process, leading to a well-informed decision. Ultimately, investing in the right heat pump guarantees an extended swim season, reduced energy costs, and a more sustainable, year-round pool enjoyment. 


Pools shouldn’t remain unused for half the year; heat them properly to enjoy them year-round!

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