Above Ground Pool Heater 101 (How to Buy The Best One)

It is worth considering whether you should heat the pool to extend your pool season. But which pool heater is suitable and how much does it cost to heat a pool?

The pool water can be heated with the heat pump, an oil and gas heater combined with a heat exchanger, or a solar pool heater. Solar pool heaters are particularly economical and trendy, but a solar cover should also be used for all systems.

In this article, you will learn different ways how to heat a pool as quickly as possible. You will also find helpful information how to install the heater system.

Heat the pool with a reversible heat pump

The pool heat pump (ASHP) is one of the active systems used to heat a pool and is much more economical than a standard electric pool heater.

This means that 70% of the energy is obtained from the ambient heat, and 30% must be supplied electrically. This achieves a high efficiency of 1:4 when you heat the pool.

The advantages of such a pool heater are the short heating-up time for the pool water and the space-saving installation option in the garden.

In my pool heater comparison, I compared the efficiency of the reversible heat pump and showed that it can reduce energy costs by 50%.

But how does the reversible heat pump work?

The reversible heat pumps contain a liquid medium that evaporates by the ambient hot air.

The integrated compressor generates pressure with the help of electrical energy and brings the steam to a higher temperature.

The generated heat is then transferred to the pool water in a condenser before flowing back into the pool. The medium itself cools down again, becomes liquid, and returns to the initial stage – a closed cycle is created.

Enough for the theory!

Which heat pump for the pool is the right one in practice?

So that the pool heat-up times stay short and energy is not wasted unnecessarily, I recommend always a more powerful heater.

In a swimming pool with around 40 m³, the output of the reversible heat pump should not be less than 8 kWh.

If a salesperson calculates and offers you a pump with less power, you can assume that he only wants to make sales.

A weak pool heater leads to high energy consumption and long times until the pool water is heated-up.

Compare different manufacturers and prices. Another heating system may make more sense for your pool.

If you just want to heat the water in a kiddie pool, I recommend my article on this topic. Just follow the link.

Tip: Always use the pool heat pump with a solar cover to prevent heat loss and save additional energy.

Use an oil and gas heater for the pool

Another method to heat the pool water is to use oil and gas heaters in combination with a heat exchanger.

Like the reversible heat pump, this system is also part of the active heating system for the pool.

The practical thing is that the heat exchanger can be installed on an existing heating system in your house. Of course, installing the heat exchanger on a separate system is also acceptable.

A pool can be heated by up to 50 °F (10 °C) in 24 hours – with a heating output of approx. 40 kW.

But how does the heating system with oil and gas work in combination with the heat exchanger to heat the pool water?

The heat exchanger is an interface between the water circuit in the pool and the heating system.

Heated water from the heating system flows through the heat exchanger and heats the pool water without mixing with it.

A heat exchanger compatible with an oil and gas heater is available for around 500 dollars. However, the costs for installing the system must also be included in the calculation.

Electrical heat exchangers that are in the same price range are also interesting. However, these are only recommended for those who purchase cheap electricity.

How quickly the pool water is heated naturally depends on the performance of the respective heating system. A comparison of the heating-up times and the resulting costs can be found below.

Heat the water with a solar pool heater

If you are looking for a passive method to heat the pool water, you can install special solar systems for the pool.

There are different collectors to heat a pool with solar energy, but in particular, two types are to be emphasized:

  • Absorber systems: The black plastic absorbs the heat from solar radiation and transfers it directly to the pool water.
  • Vacuum tubes: A vacuum tube collector consists of evacuated glass tubes and contains a heat carrier in the center that heats the pool water. The double-walled Sidney system is particularly recommended for heating a pool.

In the ideal case, the angle of the system to the sun is between 35 and 90 degrees.

Important information when installing a solar pool heater

The following instructions must be observed during the installation of a solar pool heater.

  • The size ratio between the collector and the pool surface must match so that the haet-up times remain within reasonable limits. The bigger the solar collector, the better.
  • A more powerful pool pump is required if the solar panels are installed on the roof. Pay attention to the head information – you can read more about this in my pool pump test.
  • A powerful pool pump also favors the heating of the pool water and prevents the skimming from worsening due to the installation of the solar collectors.

Combine the solar pool heater with a solar control

Combining the solar system with a solar control system is also an option.

The solar control is useful and ensures that the water flow passes through the absorber and back into the pool as required – this increases the efficiency.

According to the manufacturer, the generated heat increases by 80% with a control device. However, these values ​​are only achieved on hot summer days from June to July.

An efficiency of 45% on average can be expected in spring (April). The same goes for August.

You can find more about the efficiency of solar pool heaters compared to the other pool heaters in my pool heater test, linked above.

Tip: Many advisors recommend a second pool pump if you use a solar collector. This can be avoided by installing the collectors from the multi-valve and heating just the filtered water.

Heat the pool water with the solar cover

The solar cover is another passive way to heat a pool.

Manufacturers of solar covers for the pool talk about a temperature gain of up to 50 °F, but 35 – 38 °F is the reality.

Especially in small above-ground pools, solar covers are a popular way to protect the pool from cooling down.

Those with small air bubbles have proven to be the best – preferably black or blue.

The function of the solar cover is simply explained.

The mat is stretched over the pool surface, absorbs the solar energy, and transfers the heat directly to the pool water – of course, the pool’s location and southern orientation play a significant role here.

  • The advantage of such a pool cover is that no electricity is required to heat the pool.
  • The disadvantage is that the temperature gains depend entirely on solar radiation.

A solar cover is inexpensive, but in practice, it should always be used in combination with another pool heating system, such as a heat pump or solar pool heater, to minimize heat-up times.

Furthermore, energy savings to 50% can be expected by using the solar cover.

Note: Regardless of which pool heater you choose, a solar cover should always be used to prevent heat loss and save energy.

Tips and tricks on how to heat the pool

There are many factors to consider when you choose a pool heater.

But what is neglected in guides is the correct pool heater installation and possible cost savings through simple tricks.

The following chapter explains how the swimming pool heater should be installed in your pool and how to save costs.

Proper installation of pool heaters

Even beginners can quickly connect a simple solar collector to the water cycle.

The proper connection of collectors on the roof combined with a heat exchanger is more complicated.

On the other hand, the connection of the oil and gas heater to the water circuit of the pool should only be made by an expert.

Whether you opt for a solar pool heater or a reversible heat pump, the pool heater should always be connected to the existing water cycle.

This is a simple trick that many experts do not recommend, but it is essential to save a second pool pump and not affect the filtration performance.

In addition, the placement of the pool heater at an appropriate point is also crucial.

Ideally, the pool water – that has already been filtered – is heated between the multi-valve and the return nozzle.

Tip: A 3-way ball valve and a suitable control device can increase the efficiency of the solar pool heater when the absorber circuit of a pool is automatically closed and opened.

Build a pool heater yourself

Maybe you are also interested in how to build a pool heater yourself?

With little skills, the right equipment, and the help of the video instructions, this shouldn’t be a problem.

Only dare to use the DIY pool heater if you know what you are doing – it is well known that you do not play with fire and water.

Do you have any other questions about how to heat the pool?

Contact me at @contactswimfool on Twitter, Facebook, YouTube, and other popular social media. I am happy to help you personally.

Have fun heating the pool!

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Hi. I'm Max Berg. I've been in the pool industry since 2015 and have always felt drawn to water. I'm the author behind swimfool.com, where I share my years of experience in pool maintenance and give helpful tips on keeping a swimming pool or hot tub clean. My tips reduce the costs of water treatment and protect the environment.

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