Solar Pool Heaters – The Ultimate Guide

One of the common nuisances of having an in-ground pool is the water temperature – it just won’t stay warm! Water is not that well known for storing heat over long ​periods. If anything, it is known for exactly the opposite – it transfers heat. As pools have a large surface area, the heat loss here takes place even faster. Like air, hot water tends to surface upwards and radiates the heat to the surrounding. Solar pool heaters are just right to solve this problem efficiently.​

​During the summer, ​​most people would prefer cool water. But the depth after about 10 inches from the surface might not match your expectation of ‘cool’. The bottom layers of the pool water ​can be quite chilled. Plus, as you enter the pool, the body is more sensitive to the cold due to the sudden ​temperature change. The reason why water is so notorious is, it tends to maintain a constant temperature around 70 degrees Fahrenheit. Also, water has a high specific heat capacity - the amount of energy required to raise the temperature of one gram of water by one degree Celsius. Which means a lot of ​energy is needed to warm up ​such a high volume of water inside a pool.

This is why you would a need a pool heater. But since all heaters work using the generic mechanism, a pool heater would consume a hefty amount of power. And this is why you would need a solar pool heater. ​Here we attempted to address some of the most relevant, common questions and prepare the ultimate guide for solar pool heaters.

How does a solar pool heater work?

The mechanism is pretty simple. The components of a typical solar pool heater includes a solar collector, a filter, a pump and ​control valves. The solar collector is a series of mats with veins through them, that are laid out in an area that gets direct sunlight. These mats absorb heat.

First, you set a temperature you want using the digital controller. There are sensors that detect and report the pool’s and the solar collector’s temperatures to the controller. When the difference between the two readings are above 7 degrees, the controller turns the pump on.

Then, the pool water is pumped through the filter and then through the solar collector veins, where heat exchange takes place as the water flows through. The warm water is then circulated back to the pool and the process continues until the desired temperature is reached.

​The 3-way valve in this case bypasses the water flow away from the collector and back to the pool when necessary. This happens when collector is at ​the desired temperature or at a much higher ​one than the pool’s.

How to Install a solar pool heater

Solar pool heaters come with their own set of instructions from the manufacturers. But the basic steps are usually similar and outlined below.

Before setting on installing one, determine the location to lay out your solar collectors. The most common spot is the roof of your house, but ​some people build a separate shed or platform on which the collector panels are spread out. A land slope could work also. Make sure the area is exposed to ample sunlight and is elevated than the pool.


Once you figure that out, measure the solar collector panels and mark out the spots where you would like to mount them. The installation kit usually includes all the required hardware, but you might still need a drill, some caulking and an assistant.

Start with the collector panels. Unbox them and connect the pieces accordingly after laying them out on their designated location. Mount the panels on the platform using the provided hardware and secure them in place appropriately.

Next, move on to the pipes. According to the system schematic below, you are supposed to place the valves on the pipe at locations after the pump and filter. In this case, it has a check valve and a 3-way valve. But it could vary according to different brands. The idea of the check valve is to prevent any back flow. The 3-way valve is there to divert the water from the collector when necessary. Cut the pipe at the proper location and install the appropriate valves included in the package.


After the 3-way valve, you are now to attach another pipe. It could be a T-pipe or two separate pipes, whichever fits your situation. The objective is to make one way for the water to go up to the collector and another way for the water to be bypassed. If there are any additional valves to be placed, do so now.

Then, connect the feed line and the exit to the collector panel - the return pipe is usually connected towards the top of the panel and the feed pipe at the bottom. And this is basically it.

As mentioned earlier, every product is different and follows their own protocol. So do read the instruction manual for 100% accurate information. What we outlined here is just the general concept. 

How to winterize solar pool heater

Winterizing a solar pool heater is fairly simple. There are no special requirements as long as the collectors and plumbing have been installed properly, allowing the system to fully drain out after each use. When water freezes, it expands. So any water remaining inside would freeze and expand, damaging the system eventually.

If you have a self-draining heating system, there is nothing more you need to do other than turning the system off. If not, start by turning the circulating system off and allowing the solar collectors and piping to drain completely.

Then, ​isolate the connection to the collectors by engaging the ball valve and check valve in the return line accordingly, so that the bypass position is on now. ​After the pipes have been drained out fully, you can use a blower or air compressor to remove any remaining water from the pipes. Finish up by making sure everything is dry and free of any moisture.

How much does a solar pool heater cost?

The complete expense behind a solar pool heater depends on several factors – the pool size, the area in question, the placement of the collectors, the amount of time you run the system, etc. There is a wide range ​for the cost of a heater, and it varies accordingly. Here, we tried to give a general idea.

The system alone ranges from $2500 to $9000 depending on your need and the type of mats. The average cost ​lies around $5000.

Installation charge can fall anywhere between $500 to $1000, again, depending on the pool size and the amount of work needed.

While the heating only is free of charge, it will cost you some money to run the water through the pump. Depending on your pool size, you can expect a monthly charge of $50 to $250 in your utility bill ​for running the pump.

Are solar pool heaters effective?

Definitely. If you have the correct sized system installed, you can increase the pool temperature significantly on a sunny day. You can also boost the water temperature higher than the surrounding temperature to retain some extra warmth before the sun sets.

Plus, solar pool heaters not only works on bright, sunny days, ​they can also work in warm, overcast days, even if the sun is somewhat clouded - 'warm' being the keyword. The exception ​is rainy days or chilly, cloudy days, when the ambience is cold altogether.

Does solar pool heating work in winter?

​Partially, yes. It is definitely not as effective ​as in summer, but there could be days during the winter season when a solar pool heater can serve. As mentioned above, the keywords here are warm and sunny.

​During winter, as the days are shorter and sunlight is not as much available, there is not much the solar collectors can work with. But, the occasional bright and temperate days during the season can be favorable for the system and the pool. ​If you are residing in areas with frequent, continual snowfall, you better not have high hopes and rather winterize your system for the while. But for people living in the southern parts or areas with less frequent snowfalls, you could be in luck certainly.

TL;DR - Solar pool heaters can surely work winter if there are sunny and tepid days, but not as efficiently as in summer.

D​id you find this article useful? Did we miss out any point?  Let us know in the comments!

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