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Choosing the most sustainable solution for your outdoor pool

7 min read
Insights Content Sustainability 2

Heating an outdoor pool is an energy-intensive process, so it is important to employ a solution that keeps costs at a minimum. Here, we discuss the difference that can be made through a Calorex inverter heat pump and how to use it optimally.

An outdoor pool can be an attractive addition to any home with the space to facilitate one. The idea of a relaxing, refreshing dip surrounded by the great outdoors is a feeling that many homeowners can get on board with – for others, it is already a reality.

However, in order to deliver the experience that many visualise when establishing their outdoor pool, keeping the water temperature at a comfortable level is essential. And, for outdoor pools especially, an inefficient or inappropriate heating solution can cause energy costs to skyrocket.

This article will outline the value that an inverter heat pump can offer in terms of enhanced energy efficiency, and what steps you can take to ensure your outdoor pool is managed in the most sustainable, cost-effective way possible.

Heating an outdoor pool vs heating an indoor pool

Heating is the greatest source of energy consumption for an outdoor swimming pool by far, and much of this is to counteract evaporation. Through our research, we have determined that between 80% and 90% of the heat delivered to a pool is there to offset the amount of heat lost through evaporation.

It is for this reason that the burden of heating an outdoor pool is typically much greater than an indoor pool. In a well setup indoor pool environment, it should be possible to maintain the surrounding air temperature 1-2ºC above the water temperature. This restricts the amount of evaporation that will occur, and therefore minimise heat loss.

With an outdoor pool, you have no control over the climate and weather. Depending on where you live, the air temperature can be significantly below the water temperature, which will encourage more evaporation and, consequently, make the pool colder. Plus, wind can steal the water vapour from the surface of the pool, making evaporation an even bigger issue.

This emphasises the need to utilise a heating solution that is sustainable and energy-efficient as possible, to manage outdoor conditions and deliver a comfortable, enjoyable experience.

Harnessing heat pumps over gas boilers

The method for heating an outdoor pool is practically a one-on-one choice – a heat pump or a gas boiler.

Both have their pros and cons. For instance, an air-source heat pump is reliant on the sensible heat and latent heat available in the atmosphere to determine how much heat it can provide to a swimming pool. With a gas boiler, the output is constant regardless of the climate.

However, when you are looking for the most efficient solution, a quality heat pump is the standout option.

With a gas boiler, they will usually run at around 99% efficiency. To all intents and purposes, this means that for every 1kW of gas energy, your pool heater will deliver 1kW of heat energy.

In comparison, an electricity-powered heat pump is far more efficient. With a fixed, conventional unit, you will often see a CoP (Coefficient of Performance) of between 4 and 5. This means that, for every 1kW of electricity the unit uses to run, it delivers 4-5kW of heat energy into the swimming pool.

As you can see, this is markedly more efficient. And, as we will discuss shortly, this efficiency can be increased even further by the use of inverter technology.

When this technology is combined with a renewable energy source such as Solar PV (Solar Photovoltaic), which is becoming increasingly more common, the choice of a heat pump as a sustainable solution is a no-brainer. By generating your own electricity through this approach, you can essentially run your heat pump for free, while still receiving its enhanced COP.

In addition, from an installation perspective, an electric heat pump is far simpler to install and maintain over time than a gas equivalent. The installation and maintenance of a gas boiler heater must be conducted by a gas-safe qualified engineer. Conversely, a heat pump can be installed and maintained by any qualified electrician.

As there are fewer gas-safe engineers than electricians, their services will typically be more costly, which will impact both initial installation and any future maintenance performed on the unit.

The value of an inverter heat pump

In recent years, inverter swimming pool heat pumps have become increasingly sought-after. Through this technology, the COP of the heat pumps rises to around 10 on average. The Calorex I-PAC range for instance gives an average COP of 9.7, while the V-PAC solution rises to 10.7.

By delivering approximately 10kW of heat energy for every 1kW of electricity, this represents a super-efficient solution for heating an outdoor pool, making this approach significantly more sustainable.

Furthermore, inverter technology automatically adjusts how it is operating based on the conditions of the pool. With a traditional, conventional heat pump, the unit is either on or off. This means it will use the maximum energy necessary to get the pool to the desired temperature, switch off once this is achieved, then turn back on when the temperature drops to a certain point.

Conversely, inverter technology will run at max capacity to heat the pool initially then, rather than shut down entirely, will slow down. It will modulate its speed until it finds its optimal control point – where the exact amount of heat it provides is off-setting the amount lost through evaporation – and stay at this level. It.

Moreover, it will adjust based on changing conditions. For instance, if a pool cover is removed, leading to a lot of immediate evaporation, or more people get in and out of the pool, an inverter heat pump will automatically determine how much heat it needs to provide to maintain the desired temperature. The relationship between how hard a machine works, (how much power it needs), and it’s performance is exponential, so slowing down a heat pump reduces the cost of use dramatically.

This offers several great benefits:

  • While running at slower speeds, the energy usage of these units is greatly reduced (e.g. if running at half-speed, the heat pump will be using ⅛ the energy it would use at max speed)

  • A consistent temperature is maintained throughout the pool’s usage, providing the ideal comfort for the users

  • At slower speeds, the inverter heat pump is quieter, creating a more comfortable environment overall for both users and their surrounding neighbours

Additional steps to a more sustainable outdoor pool

Hopefully, this has demonstrated the increased energy-efficiency that can be achieved through the use of an inverter heat pump. The efficiency of this technology has made them a valuable asset for both domestic outdoor pools and, to an increasing extent, lidos and commercial outdoor pools.

Nonetheless, creating the most sustainable outdoor pool setting extends beyond the heat pump itself. It also relies on how it is positioned and how you look after your pool long term. Here are some key tips to help you cut down on energy consumption further:

Apply a pool cover when the pool is not in use

A pool cover is your best defence against evaporation when a pool is not in use. By applying one during these periods, this both limits the amount of times you need to refill the pool and lessens the load on your heat pump.

Check for and address any leaks

If your pool has sprung a leak, this may mean you are having to refill your pool more regularly. By adding this colder water from a tap or other source, it means your heat pump has to run at a higher capacity to heat this to the desired temperature.

Keep the heat pump open to the air

Heat pumps are not always the most aesthetically beautiful units. But, if you obscure the intake and/or outlet in an attempt to keep it out of view, this will likely reduce the amount of warm air that it can access to heat your swimming pool, limiting the level of heat it can deliver into the pool itself.

In addition, if the unit is kept in an enclosed space, this means that the cold air from the exhaust can be recycled back into the air intake. This can begin a vicious cycle of progressively colder air being sucked into the heat pump, eventually making its ability to heat your pool non-existent.

Choose Calorex for sustainable outdoor pools

Under any circumstances, the process of heating an outdoor pool is an energy-intensive task. However, with the right heating solution and by managing it correctly, it is very possible to limit energy consumption and run these as efficiently and sustainably as possible.

That is where Calorex heat pumps can be of assistance. With over 40 years’ experience in the design and development of heat pump technology, Calorex are the experts in this industry, creating cutting-edge products like the I-PAC inverter heat pump:

  • Average COP 9.7 (2x more efficient than on/off heat pumps)

  • Eco-friendly refrigerant R32 (675 GWP)

  • Safe to operate in air temperatures of -5°C to +43°C

  • 9-11 dB(A) sound reduction compared to an equivalent on/off heat pump

  • Integrated controller with a touchscreen user interface


For more information on our market-leading heat pump solutions, get in touch with our team through the form below.

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