We are asked frequently, why can’t one type of solar panel do everything? Specifically, people want to know if you can heat a pool with solar electric (photovoltaic) panels. With the price of solar electricity now much lower than it was just a few years ago, it stands to reason that heating a pool with electricity might now be cost effective. Can you heat your pool with solar electricity? The answer is yes, it can be done; but not directly and it is typically not the best solution.
Solar pool heating panels use solar thermal technology to heat pools. Solar radiation is absorbed and heat is transferred from the panels to the pool water within. This is a very simple and efficient process. Solar pool heating panels can convert as much as 85% of the sun’s energy hitting them into heat energy that is transferred to your pool.
Solar electric panels convert solar radiation into electricity. Using electricity to heat water is very inefficient. In fact, heating or cooling anything (water, air) requires a lot of electricity, and the conversion process is inefficient. Furthermore, solar electric panels commercially available today range in efficiency from 14% – 21% efficiency, far lower than the 80%+ achieved by solar pool heating panels.
If you wanted to heat your pool with solar electricity, you would also need a mechanical means of doing so. That means you also need to buy an electric heat pump. A good heat pump alone costs as much as a solar pool heating system — and you still need the solar electric system, which is very costly relative to solar pool heating systems. In the end, an investment in solar electricity to heat your pool would cost in the range of five times that of a solar pool heater. While solar electric panels are long lasting, heat pumps typically require replacement twice in the lifespan of a solar pool heater, and have moving parts and electronics that are prone to maintenance requirements.
On a good note, if you intend to heat your pool only very occasionally, a solar electric system can take the excess energy produced and reduce your electricity bill. This might fit the needs of people who want to heat a pool only on rare occasions, or need to provide heating performance that solar panels alone cannot achieve. However, there is no question that the most efficient way to heat your pool is with solar thermal technology, and not solar electricity.
Can PV panels be mounted atop my pool cage instead of my house roof? It seems that it would create a shady area for my patio as it generates electricity. Can an aluminum pool cage support the PV panels?
It’s important to note that the economics are changing quickly and in some cases where you plan to run an electric heater anyway to supplement solar thermal (if you already have an electric heat pump), it might make sense to just go all electric. Financial incentives definitely complicate the decision. The nice thing about solar electricity systems is that they continue to power other loads in your house when your pool heater is not running, so there is no loss of energy. On a downside, the fixed cost of solar electricity systems makes small systems less attractive.
Jason,
I live in Fort Worth, Texas which would be at about the same latitude as Savanna or St. Augustine. I have a 30,000 gallon pool and the back of my house faces due south. I have a 4,500 sq ft house that is two story so I have a lot of uninterrupted sunlight all day. No tall trees to block the sun. My wife is a swimmer and wants to swim year round in our pool. What I’m thinking is that I place solar panels on the roof that feed the pool electric heater during the winter and then turn it off during the summer or let the excess flow back to the house to reduce the electric costs all year long. Is this a possibility with today’s technology?
To be clear, I’m not talking about running water through tubes to warm the water but rather create direct electricity that can feed to the pool and house.
Thanks
Hi Dan,
It sounds like you are overcomplicating things a bit. When you install a solar electricity system you just connect it to your whole home and it offsets your electricity bill. Just estimate what an electric pool heater will cost and a solar professional in your area can tell you how many solar panels you need to offset that amount of electricity. This is called a grid-interactive solar energy system.
Think of it this way – in the winter the solar panels will be offsetting your pool heater during the day, but if the pool heater turns off because the pool has reached the desired temperature, the solar panels will continue powering other loads in your house. It doesn’t matter whether you are powering your pool heater or another electrical load, and any excess solar production is sent back to the grid for future credit.
Jason
It seems like a great idea to create electricity and at the same time run water on the underside with water tubes incorporated in the panels. ….The water will cool the panels and heat the pool water on return by a controlled circulation pump valves….. just as you would with conventional hot water solar panels.
Pete,
It has been or is being done by a couple of manufacturers. The water cools the PV panels, making them slightly more productive. The pool water heats up, but not as much as standalone solar pool heating panels (because naturally, the photovoltaic panels siphon off some of the energy). The main problem with this is that it is very expensive with today’s technology. It is difficult to manufacture and the economy of scale is not there because it is a niche product. There is another problem that is not specific to Florida but is amplified here – at the time you need to cool the PV panels the most (summer), the pool does not need any heat. In fact, pools become too hot. So heating the pool more to make the photovoltaic panel more productive makes the pool uncomfortable, perhaps unusable.
Conceptually this is a great idea. If you have a large enough heat sink, it could work. But you need to have a need for the heat. Otherwise, you would have to run a separate pump to a heat sink, which takes electricity, and perhaps a fan, causing a zero-sum game with respect to increasing solar electric efficiency.
If you have enough roof (or ground) space, it is more economical to run separate solar electricity and solar pool heating systems. The ROI is better. If you have limited space, you might be willing to pay a premium to get a combination product. But if you are concerned with the overall value, it is a difficult proposition.
Another factor is longevity, which has not been proven out with a product like this. Remember the TV/VCR combinations of yesteryear? They generally did neither function great, and when technology improved for TVs, and VCRs became obsolete, the whole product looked like a bad buy. And what about warranty? A leaking solar pool heater is easy to fix, but when combined with a solar photovoltaic panel, a repair becomes more costly. On those TV/VCR combos you had to replace both if one component died. Add to that the fact that a limited number of installers will be familiar with the product, and you are setting yourself up for a service nightmare.
Conceptually, I love it. Practically, I can’t currently stake my reputation on selling a product like this. In climates where pools need heating in the summer when ambient temperatures are high, it makes more sense and might become economically viable. I have not done that math since my business is specific to Florida. In a commercial application where process heat is needed, there might be another viable application. But without the economy of scale, I believe it is going to be hard to manufacture a product in an economical fashion where it becomes widely recommended.
Jason – what about the concept of a photovoltaic solar panel (to generate electricity) and a water pump to use the pool water to cool the panels (making them more energy generating) and heat the pool in the process? I’ve heard of these systems being available in Europe but I’ve been waiting anxiously for them in the US. Have you heard of them?
Incidentally, the company we represent has just release such a system. There are pros and cons to this arrangement, but there is no questions that you can extract a huge energy value from a smaller footprint by doing this. The efficiency of the solar panels goes up, but the pool heating performance goes down. There is also the issue of times when you do not want the heat the pool, like in Florida summers. Give our office a call if you want to learn more. Ask for Dominick and we can get you some spec sheets.