When buying a solar pool heater, you may be surprised to find a range of suggestions for how many panels are needed to heat a swimming pool, but there are some guidelines that you can rely upon. The correct answer depends on your location, the orientation of the panels, shading impacts, the panel type, the panel performance rating, your desired performance, and more. However, no single factor is more important than the size of your swimming pool. When I say size, I am not referring to gallons, which many clients often provide as a starting point. The size we need is the surface area in square feet.
As a rule of thumb, we recommend 100% coverage, meaning you need one square foot of solar panels for each square foot of pool surface. From there we make adjustments depending on the other factors. If you have shading issues, less-than-ideal orientation, live along an open body of water (windy), or use a separated tube panel (which performs worse in winter), you will probably need more panels. If you have a perfect south or southwest roof with other ideal factors, you may be able to get away with fewer panels. You may need to use multiple orientations to fit the number of required panels. In selecting the right number of solar panels, there is as much art as there is science. A qualified solar contractor can lead you to the right decision.
Don’t worry if you don’t have enough space or if your budget does not allow a perfectly sized system. Undersized systems and systems with sub-optimal orientation will still heat your pool every day, but they may not perform quite as well as a perfectly situated system. When you get the “ideal” 100% coverage scenario, expect your pool to reach about 10 degrees Fahrenheit above an unheated pool on most days, and 15 degrees if your cover it, especially at night. Depending on the time of year and factors that make a system sub-optimal, these systems will often provide heating that is perfectly acceptable, and will still be warmer than an unheated pool.
Since an unheated pool’s temperature varies throughout the year, so will a solar heated pool’s temperature. While there is no temperature guarantee with solar pool heating, the good news is that the resulting temperatures are comfortable for swimming 10-12 months of the year for most people in Florida without any auxiliary heating when an ideally sized system is installed.
In selecting the right number of solar panels, there is as much art as there is science.
You might be asking whether installing more panels will result in more heating performance. Why not go over 100% coverage? If you install 200% coverage, will you get a 20 degree rise in temperature? The answer is no. There is a point of diminishing returns, because as the pool water approaches the panel temperature, the heating performance (efficiency) decreases. Solar thermal systems like solar pool heaters rely on a large difference in temperature (known as Delta T) to transfer heat to the pool water. For this reason, we do not recommend installing very much more than 100% coverage, although more panels will increase pool temperature faster in the morning. If you like to swim earlier in the day and demand maximum temperature, then exceeding 100% coverage may be suitable for you.
A system with an automated controller can maximize heating performance and avoid solar panels actually cooling your pool inadvertently in inclement weather. We recommend a controller be installed with every system to increase performance and customer satisfaction. A closely managed manual system can perform almost as well as an automated system, but most owners are not diligent enough to turn their solar valve when needed, and the convenience of an automated system cannot be overlooked.
We find that most pools in Florida are somewhere in the 12’x24′ to 15’x30′ range in Florida, suggesting system sizes of 288 to 450 square feet. Using 4’x12′ panels, most solar pool heating systems require between six and ten panels with seven to eight panel systems by far the most popular.
Note that these recommendations are specific to Florida, and will vary slightly between different locations within the state.
I have a 10X20 4000 gallon “spool” (combination pool with 6 jets) in Ormond Beach, FL. It is in a screened lanai facing east. How many panel would be needed to use the spool in the shoulder seasons at 80-85 degrees. [Company removed] rep is saying they sell a 3 panel minimum package…..cost = [Price removed]?
Joe,
I understand the need to have a minimum system size. There are fixed costs that make very small systems pretty expensive. You might find that adding a panel or two doesn’t increase the cost too much. Below a certain number of panels the flow rate may be too high for optimal pool heating (while a high flow rate through a solar pool heater is almost always desirable, there is a point of diminishing returns and can actually be counterproductive depending on the scenario). The type of pool you have typically has a pump with a high flow rate to provide a spa-like experience. With a 3-panel system, you may be trying to force more water through the panels than they can heat, and high pressures may decrease the system life and increase service issues. There are dynamic issues at play that probably require more study than I can provide here, but I’ll make two comments that might help you.
1. The size of a solar pool heater is typically determined by surface area primarily. While your pool doesn’t contain much water, we are trying to regain heat lost from the pool, the majority of which happens at the surface. I would recommend a minimum of 4 panels each 4’x12′ for your pool surface area, adjusted for other factors which I am not aware of (orientation primarily plus several other factors).
2. The type of pool you described usually has a highly agitated surface to create a spa-like experience. This causes the pool to lose heat faster during operation, especially during cool and/or windy ambient conditions. For this reason alone I would increase the system size to 5 panels for the best experience.
I have a 25 x 10 pool how many panel will I need and can I place them on my aluminum terrace roof?
Hi Jorge,
There are too many factors to answer your question without additional information. Generally speaking, you need approximately the same square footage of the pool in solar panel square footage. This is adjusted for those other factors (orientation, pitch, wind, shade, and other factors specific to your pool. You need a local professional to give you a definitive answer. Expect the answer to be 5-7 panels. It also depends on whether you want minimal, ideal, or maximum performance. It’s a discussion you should have with a professional dealer. We do not recommend installing on an aluminum terrace roof. The structure is usually not sufficient. Solar panels are usually engineered to be installed on manufactured truss roofs. There is also the matter of how to properly waterproof each roof type. Your specific roof would need to be evaluated. Again, it’s not recommended.
Can you stand these panels on their side and affix them to a rod yard fence which would then face southern direction?
Hi Steve,
The short answer is – no. Solar pool heating panels are not designed to be installed horizontally. There is no support system for this, and the headers need to be top and bottom for parallel plumbing and drainage. Also, at least here in Southwest Florida, a fence would not be nearly strong enough to handle the design wind loads imposed on the solar panels.
My house has 2 levels and its made of concrete. Our living space is mostly concentrated on the second level. I have 2 questions;
1. Will the pump need to work harder to get the water up to the roof and therefore consume more electricity?
2. Will these panels generate additional heat on my roof thereby making the house warmer?
Hi Tony,
The complete opposite is the answer. Here is why:
1. If you have a single-speed pump, which I am assuming here, the pressure on the outlet of the pump will increase slightly. I say slightly because water must be lifted to your roof, but then it falls back down, so there is a siphon effect involved. There is also friction involved, so the relationship is complicated. But generally the increase in pressure is 1-5 PSI depending on your scenario. Now when the pressure goes up, flow rate goes down. In essence, from a physics perspective, the pump is doing LESS work, not more. There is a little more to it than that, but the net result is no change in your pump energy consumption, or at most, a negligible change. If you are talking about a variable speed pump, that is a whole other story, but generally speaking, a properly reprogrammed variable speed pump will result in a small increase in pumping costs when you are heating the pool, but it is very minor in the grand scheme of things.
2. The solar panels will COOL your roof! The cooler pool water running through them will extract heat from the roof surface and transfer it to the pool. The hotter your roof (and attic), the more heat will be extracted. Now I would not count on this being noticeable. The amount of heat transferred in this manner is very small in relation to the latent heat in the building as a whole. If your solar panels are not operating and are void of water, they will “attract” more heat than a lighter colored roof, but the air inside is a good insulator. And you also get the benefit of the black panels at night emitting heat to the night sky. The panels have a higher emissivity than your lighter colored roof. The short answer is that solar panels will not increase the temperature inside the building as a whole, and will not damage your roof due to increased heat.