Solar Pool Heater – How To Choose The Right One

A solar pool heater in temperate and cold countries is certainly a boon. It extends the usable period of a swimming pool by preventing the pool from freezing up and by keeping the water warm enough to swim in.

More importantly, it does so at no cost as the energy used is free. This means that there are zero heating costs compared with using an electric or gas heater. This translates to a tremendous amount of savings for public pools. It means more income too, since it allows the pool to operate 24-7 throughout the entire year.

However, picking pool solar panels isn’t as simple as buying a T-shirt in a mall. There is a wide variety of solar pool heating solutions. Some of them come with a hefty price, some are very affordable.

More importantly, the solar pool heating system should match the set-up of the swimming pool and the building or house. Otherwise, it will defeat its purpose and end up being a less than optimal investment.

This article explains what you should look into first when deciding on the type of solar pool heater. From there, you’ll be able to pick the perfect one for your needs.

How to select a solar pool heater?

Before you purchase and install a solar pool heating system, you should answer the following questions:

  • Will you be using the solar pool heater during frigid winters?
  • What is your site’s solar resource for the pool heater?
  • What is the correct solar pool heating system size for your pool?
  • What is the best orientation and tilt for the solar collector?
  • What is the solar heating system’s efficiency?
  • Have you compared solar pool heating system costs?
  • What are the local codes, covenants and regulations for solar pool heaters?

Unless you’re a maverick at solar, answering all these questions on your own can get overwhelming. You might want to engage a local solar system supplier or installer to assist you, but at least these questions will give you a guideline. Solar system contractors determine system requirements and collector sizing using worksheets and computer programs.

Will you be using the solar pool heater during frigid winters?

Will you be using the solar pool heater during frigid winters
Photo by Roan Lavery on Unsplash

In frigid winters, you would expect the swimming pool water to freeze. Depending on where you live, this could mean the pool water is frozen for half of the year. Even if the water does not freeze, some places are so cold that it is almost impossible to swim in autumn or early spring.

For such places, it is better to opt for a glazed solar collector system. This isn’t to say that an unglazed one cannot be used, but a glazed system is more effective at absorbing solar heat.

Nonetheless, whether glazed or unglazed, the solar collector should be winterized (including freeze protection) if it is going to be used in a climate where temperatures drop below the freezing point.

What is your site’s solar resource for the pool heater?

No matter how efficient and well-designed a solar pool heater is, its performance is inevitably affected by how much of the sun’s energy your location receives. Your place doesn’t need to have warmth and sunshine. This would defeat the purpose of having the solar pool heater.

A solar pool heater can make use of direct light and diffuse solar radiation. However, the spot where you intend to install the system should have unimpeded exposure to sunlight. This means no shaded areas.

Some places experience a drastic temperature shift between night and day, such as in or near deserts. To maximize your pool heating, you could add a pool blanket to ensure chilly temperatures during the night do not undo daytime solar gains. This is especially relevant for in-ground pools, as these lose heat faster than above-ground pools.

What is the correct solar pool heating system size for your pool?

This is the general rule: the surface area of the solar collector should be 50% to 100% of the surface area of the swimming pool. The ratio may need to be increased in cooler and cloudier areas.

The higher the collector square footage, the longer the swimming season. To decrease the required collector area, you can use a pool cover.

The system size is also affected by your average regional temperature and preferred pool temperature. The higher the difference, the bigger the system size.

What is the best orientation and tilt for the solar collector?

For those who live in the northern hemisphere, the best direction for the pool solar panel so that it faces the sun is generally south. This applies to solar pool heaters that are mounted on the ground or on the roof.

The southward range is effective up to 45 degrees west and east of true south. Just make sure nothing in that direction will block sunlight during the daytime.

Next, you need to consider how much space you have for the pool solar panels. Some solar pool heaters need a massive amount of space. If you don’t have the space on the roof or the ground, you might have to opt for other types of solar gadgets for heating pools.

The tilt of the solar collectors or pool solar panels depends on your latitude and length of swimming season. For summer only heating, tilt them at an angle equal to your latitude minus 10 to 15 degrees. For year-round heating, tilt them at an angle equal to your latitude.

There are some opinions that the solar collector tilt does not significantly reduce system performance. If you are of this opinion, just be sure to take the roof angle into account when sizing your system. Also consider whether your area experiences strong winds.

What is the solar heating system’s efficiency?

You can find out the efficiency of the solar heating system based on the solar collector’s thermal performance rating. It is measured and shown in a few ways:

  1.       Btu (British thermal unit) per square foot per day or Btu/(ft2day)
  2.       Megajoules (MJ) per square meter per day or MJ/(M2day)
  3.       Btu per day, which is simply the rating in Btu/(ft2day) multiplied by the area in ft2
  4.       MJ per day, which is the rating in MJ/(M2day) multiplied by the area in M2.

The higher the rating number, the better the efficiency. Nonetheless, determining factors such as weather conditions, instrumentation accuracies, and other test condition constraints vary. Thus, the thermal performance of any two collectors should be considered roughly the same if their ratings are within 25 Btu/(ft2day) of each other.

Go for a high efficiency solar collector as it will reduce your annual operating costs and cost you fewer square feet of collector area to heat the pool.

You should also have a properly sized pool pump for the solar system for it to work efficiently. Think of it as the heart organ of a human body. The bigger the heart, the more water it can pump.

Have you compared solar pool heating system costs?

There are many ways to go about heating a pool with solar power. Installing a whole new solar pool heating system is not the only solution. There are cheaper options or solutions which involve adding on components to convert an existing one to a partial or complete solar solution.

To compare costs fairly, you should look at the Btu cost per day instead of just the cost of the solar pool heating system. Get an example of how to compare the cost of solar pool heaters in a separate article.

What are the local codes, covenants and regulations for solar pool heaters?

As with solar water heating systems, there are local building codes and regulations for solar water heating as well. It is in your best interest to check them out before deciding on the type of solar pool heater you want to install.

Working of solar pool heater

Do you know that the energy contained in sunlight is more than 1,300 watts of energy per square metre?

In the simple sense, solar pool heaters work by absorbing the energy of sunlight and using it to pump the water present in the pool, passing it through a group of solar collectors and warming it.

A well designed solar pool heater helps to provide real value and warmth in cold temperatures.

The greatest challenge associated with a solar pool heater is maximising efficiency. However, if the amount of sunlight received is scarce in your area, you will have to supplement a heat pump or gas pump model.

Components of a solar pool heater

Here are some of the important parts of a solar pool heater:

1. Solar collector

The water gets to the heater by circulating through the solar collector. This is usually available in two different variants:

  • Glazed collectors: Use an aluminium plate or copper tubing. The covering is usually iron tempered.
  • Unglazed collectors: These are heavy-duty plastic or rubber panels. Unglazed collectors are often UV treated to improve durability and protect them from damage. These collectors are cheaper when compared to the glazed ones.

2. Flow control valve

Diverts the pool water into the solar collector for heating. Available in manual and automatic options.

3. Pool filter

Helps to remove the mud and other debris in the pool water before it is pumped for heating.

4. Pump

It helps pump the pool water through the filter and collector and then back to the pool. Solar heater often needs a powerful pump, and you need to replace your existing pump with a powerful one.

Installation of solar pool heaters

Installation of solar pool heaters
Source: FAFCO, Inc

The proper installation of a solar pool heating system depends on many factors. These factors include solar resource, climate, local building code requirements, and safety issues. Therefore, it’s best to have a qualified solar thermal systems contractor install your system.

Maintenance of solar pool heaters

After installation, proper maintenance can keep the heater running smoothly for 10 to 20 years. Refer to the manual for maintenance requirements.

The solar collector usually requires little maintenance if the chemical balance of the pool water and filtering system are checked regularly. Glazed collectors, though, may need to be cleaned in spots where rainwater does not fall to provide a natural rinse.

Selecting solar pool heater contractors

Here are some additional questions you can potential contractors for installation or maintenance:

  • Does your company have experience installing and maintaining solar pool heating systems?
  • How many years of experience does your company have with solar heating installation and maintenance?
  • Can I have a list of your past customers who can provide references.
  • Is your company licensed or certified?

Some states may require a valid plumber’s and/or solar contractor’s license. Check with your local city and county, and confirm the licensing with your state’s contractor licensing board.

Can I DIY my solar pool heating system installation?

Since a solar pool heating system installation involves roof heights, water and large materials, it is best to leave it to the professionals. This not only protects you from any kind of liability, but it will ensure the solar pool heating system works at its best.


DIY installation isn’t advisable unless you are a qualified plumber and/or solar installer yourself as explained above. A professional will be able to help you choose and install the right solar pool heater for your needs. That being said, you can ask the professional certain questions to help you make the right decisions.

Leave a Reply