How Do Solar Pool Heaters Work? Breaking Down the Mechanics

Written by Michael Dean
June 8, 2023

solar pool heater mechanics

Solar pool heaters have grown in popularity recently because they are eco-friendly and cost very little to run. Whether you have a solar pool heater or are planning on getting one, it is helpful to understand its basic mechanics.

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 the pool water.
  • The solar collector is responsible for storing and heating pool water.
  • There are two 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 work similarly.

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. Here’s a deeper explanation of how solar pool heater plumbing works.

How Does the Plumbing Work?

Your solar pool heater uses the pool’s existing plumbing to connect to the swimming pool system and heat the water.

Diagram: 1) Solar panels, 2) Temperature sensor, 3) Solar controller, 4) Pump, 5) Filter, 6) Check valve, 7) Auto valve, 8) Heater, 9) Salt cell, 10) Return, 11) Intake

The solar collector uses the pool pump to transport water 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 the plumbing valves, which flows back into the pool through the return line.

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

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

Types of Solar Collectors

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

Flat Plate Collectors

The flat plate collector comprises an insulated metal box containing 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 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 collector comprises 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 produces a superheated vapor, reaching temperatures of 300 degrees.

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 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 to determine how much space you will need is to determine 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 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 nine 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 several 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 a typically cold and snowy area, 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

You can maximize your solar efficiency in numerous ways 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 from entering the absorber plate, reducing the efficiency of the solar heater. Water and a light cloth are 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 maximize your heating system’s efficiency. 

Need to Install a Pool Heater?

I partner with HomeAdvisor to help you find the best swimming pool heater installers in your area. Compare quotes for free from fully vetted pool heater professionals.

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 pretty complex equipment, a solar pool heater will warm your pool to a comfortable temperature without increasing 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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