How Do Solar Pool Heaters Work?

Solar pool heaters have grown in popularity in recent years because they are eco-friendly and cost very little to run. Whether you have a solar pool heater yourself or are planning on getting one, it is useful to understand the basic mechanics of how they work.

In this article, I will cover how solar heaters work and answer other frequently asked questions about these energy-efficient heaters.


Main Takeaways

  • Solar pool heaters use direct sunlight to heat pool water.
  • The solar collector is responsible for storing and heating pool water.
  • There are two different types of solar collectors: flat plate collectors and evacuated tube collectors.
  • Solar pool heaters use the pool’s existing plumbing system. 

How Do Solar Pool Heaters Work?

Although solar pool heaters differ from model to model, they all generally work the same way.

Solar pool heaters collect warmth from the sun’s direct rays and store this heat in the solar collector, which is found inside the solar heating system. The solar collector is responsible for storing this energy and warming the pool water.

Types of Solar Collectors and How They Work

There are two different types of solar collectors and both have different functions.

Flat Plate Collectors

The flat plate collector is made up of an insulated metal box that contains rows of flow tubes and an absorber plate. The outside of the metal box is usually covered in a transparent glazed material. Low iron safety glass is commonly used, which acts as insulation.

How Do They Work?

The transparent cover traps large amounts of direct sunlight through the absorber plate. And inside the absorber plate are tiny metal strips that help warm the water.

While the absorber plate collects heat, pool water coming from the inlet pipe regularly circulates through the flow tubes and gets heated. As the water circulates through the tubes inside the collector, it eventually comes out of the outlet pipe, then flows back into the swimming pool.

Evacuated Tube Collectors

Evacuated tube collectors are more expensive but also more efficient. This type of collector is made up of multiple glass tubes that house smaller glass tubes inside them. These tubes are connected to a copper header.

How Do They Work?

Unlike the flat plate collector, the evacuated tube collector does not heat water directly from the tubes. Instead, it works by removing the air between the smaller and larger tube, creating a vacuum. This vacuum insulates the heat and creates a superheated vapor, which can reach temperatures of 300 degrees.

How Does the Plumbing Work?

Connecting your solar pool heater to your pool is a relatively simple plumbing procedure as it uses the pool’s existing plumbing.

The solar collector uses the pool pump to transport water up through the pipes and plumbing valve and through the inlet pipe of the solar collector. The warmed water then exits through the back of the solar heater and through the plumbing valves where it flows back into the pool through the return line.

Inside the pipes are flow control valves; these valves are what divert the pool water through the solar collectors and back into the pool

If you want to see a visual and learn more about the plumbing behind solar pool heaters, here’s my article on solar pool heater plumbing.

How Much Space Do You Need?

The size of your pool and the temperature you want to raise your pool water will determine how much space you will need for your solar pool heater.

In general, the bigger your pool is, the larger your solar heater will need to be. A good way of determining how much space you will need is to work out how many collectors you’ll need.

How Many Solar Collectors Do You Need?

The number of solar collectors you will need will be determined by the size of your pool and the type of collector you have chosen to use. Evacuated tube collectors are the most efficient, so you will need fewer than if you were using flat plate collectors.

A basic way of working out how many solar collectors you will need is to make sure that the surface area of your solar pool heater equals at least 50% of the surface area of your pool.

For example, if your pool is 50 square feet and each solar collector is 3 square feet, you will need about 9 solar collectors to efficiently heat your pool.

How Effective are Solar Pool Heaters?

Solar pool heaters are very effective at heating pool water.  The level of effectiveness is influenced by a number of different factors like: 

  • Size of the pool
  • Location of the pool
  • Climate or weather in the area
  • Size of the chosen solar pool heater, such as the surface area covered
  • How much you are willing to spend on installation

All these things influence how effective you may find solar pool heaters. For example, if you live in an area that is typically cold and snowy, then you will find that solar is not as effective as electric heating. 

For a more in depth explanation of this topic check out my article on solar pool heater effectiveness.

How to Maximize Your Solar Efficiency?

There are numerous ways that you can maximize your solar efficiency to get the most out of your solar pool heating system.

  1. Start by keeping the solar panels clean. Dust, debris and dirt can easily block sunlight entering the absorber plate, reducing the efficiency of the solar heater. Water and a light cloth is all that is needed to clean them.
  2. Make sure that any tree branches near the solar heater are trimmed regularly. By trimming back the branches you allow for direct sunlight to reach your solar heater.
  3. Install a solar pool blanket. The solar pool blanket floats on the pool’s surface, absorbs sunlight and heats the pool water. Using one of these in conjunction with a solar pool heater will really maximize the efficiency of your heating system. 

Need to Install a Pool Heater?

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Bottom Line

Now you will really know how your solar pool heater works. Understanding your solar heater will allow you to identify any problems that may arise and maximize its efficiency. Although they are quite complex pieces of equipment, a solar pool heater will warm up your pool to a comfortable temperature without driving up your energy bill. Feel free to check out my related reading section below for more information on solar pool heaters. Happy swimming!

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