How Does a Heat Pump Pool Heater Work For Your Pool

Written By Timothy Te

10th May 2021

To better understand why pool heat pumps are the best choice for efficiently heating your swimming pool, we must answer the questions, how does a heat pump pool heater work. By answering this question, it will become clear why it saves on energy consumption and of course, you can make a better decision on whether to go ahead with a pool heat pump or go to the traditional heater route.

Pool heat pumps in a nutshell

The simplest way to describe how a pool heat pump works is that they draw in the warm air from around the unit, and transfer the heat to the water before returning it to the swimming pool. There is no actual heat generation involved so energy consumption is kept at a minimum. Now if that explanation isn’t enough, then you’re in luck, let’s go on to a more detailed explanation to how a heat pump pool heater works.

Step-by-step pool heat pump process

  • The pool heat pump fan pulls in the warm ambient air
  • The evaporator coil extracts the warmth/heat from the air
  • The warmth extracted is transferred into the refrigerant which warms it up
  • The pool heat pump’s compressor pressurizes this warm vapor into a hot gas
  • The hot gas travels through the heat exchanger which warms up the water in the chamber
  • After the hot gas releases the heat into the water, the gas turns back into liquid.
  • The liquid refrigerant gets passed through an expansion valve, cooling it even further and the process starts again


As you can see, there’s no real heat created, which is why a pool heat pump is very energy efficient, no energy is wasted! Now let’s go into a lot more detail on how a heat pump pool heater works shall we?

Pulling in Warm Air

Once the pool heat pump is turned on and water starts to flow through the unit, the fan that’s located at the top of the unit (or at the side, depending on the model) starts to spin and starts to draw in air around the unit. The air that gets pulled in passes through an evaporator coil.

Evaporator coil starts to extract the warmth from the air

The evaporator coil contains a liquid or refrigerant that can go from one end to the temperature spectrum to the other end quite easily. Once the refrigerant warms up, it transforms from its liquid form into a warm vapor or gas. Now the warm vapor isn’t really enough to warm the water so it travels through a compressor, which is the heart of a pool heat pump.

Creating hot gas from warm vapor

The compressor basically compresses (well, it is called a compressor!) the warm refrigerant vapor into a hot gas. Basically, as the pressure increases, so does the temperature of the refrigerant. So you start with warm vapor and end up with gas that is hot enough to warm up the pool's water.

Warming the water through a heat exchanger

Pool heat pumps like the ones from Madimack that Mr Pool Man carries on its online store have titanium heat exchangers which are the most efficient type out there. Not only that, but it’s also resistant to corrosion from pool chemicals and salt (if you have a salt water chlorinator). A good way to visualize a heat exchanger is to think of a tube within a tube.

There are two tubes, a smaller inner titanium tube, and an outer tube, which is basically made out of PVC. The hot gas travels through the smaller inner titanium tube, while outside the tube, water passes through and this water is contained by the outer tube. The hot gas within the inner tube transfers its heat to the water outside the tube, hence the term “heat exchanger”. The warmed up water flows back into your pool.

Expansion valves and returning into a liquid state

Once the heat from the hot gas is transferred into the water, the refrigerant reverts back into a liquid state. This liquid is still a little bit warm so it needs to pass through an expansion valve which releases all of the excess heat and turns it back into a cool liquid. Once it’s back in its original state, the process starts all over again.

No energy wasted

As we can see from how pool heat pumps work, not a bit of energy is wasted. This is why pool heat pumps have a very high COP or Coefficient Of Performance. Simply put, a Coefficient of performance so how much heat is generated in relation to the energy spent. Depending on the model type, Madimack pool heat pumps have an average COP of anywhere from 6 to 10. In a nutshell, this means that for every 1 unit of energy spent by the heating unit, anywhere from 6 to 10 units of heat are transferred to your pool.

As we can see, this is very efficient when compared with gas or electric pool heaters. How more efficient? Well, if we’re talking about new models, gas and electric heaters are required to transfer at least 70% of consumed power to the pool as heat according to Australian Minimum Energy Performance Standards. The highest efficiency gas and pool heaters can transfer up to 98% of consumed energy as heat to the pool. This is basically 1:1, which is a far cry from the COP of Madimack pool heat pumps which can go anywhere from 1:6 to 1:10!

What size heat pump do i need for my pool

There really isn’t a set size for swimming pools, it all depends on the usage type you’re planning on your pool. If you plan to constantly use your pool, then a smaller to medium sized pool heat pump will be sufficient as it is best for maintaining the pool’s temperature over extended periods of time. If you’re only going to be using your pool for once a week or less, then a larger pool heat pump would be the one for you.

You might be wondering why we’re recommending a larger pump for less usage, well, the fact is, pool heat pumps take a while to heat up your pool, and once they hit a certain temperature, maintain it. So the more you use your pool, the more efficient your pool heat pump will be. But if you don’t use the pool that much, then a larger heat pump will be needed to heat up your pool faster in between usage.

If you seldom use your pool and just want something to heat your pool on demand then you can always consider getting a traditional gas or electric heater. How can we recommend this after singing the praises of pool heat pumps? It’s simple really. If you don’t use your pool that much, then the energy efficiency of pool heat pumps will be wasted! Yes, you’re heating your swimming pool on the cheap, but if you’re not using the pool then that’s just wasted efficiency as well.

We have a more comprehensive guide on what size heat pump you need for your pool here. It has everything you’ll need from how much heat pumps cost to operate, how fast the different sizes heat up different pool volumes, and more!

Do you have any questions about this topic or the featured products? No worries, we're here to help! Drop us a question down below and we'll get back to you ASAP.

Happy swimming :)

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Written By

Timothy Te

Pool Guru at Mr Pool Man

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