Water heating takes up 12% of your energy bill. Only space cooling and heating take up more at 15 and 14% respectively. In 2021, U.S homeowners spent an average of $1,502 on electricity. This is an all-time high and prices are expected to continue to rise.
With that in mind, what steps can you take to reduce your energy bill? At present, solar is the best alternative. While it does have a high upfront cost it has a long lifespan and a relatively short payback period.
Solar water heating is an excellent and cost-effective way to start with solar energy. But can you use solar to heat your pool? How many solar panels would you need? Let’s explore these questions.
Do Solar Panels Heat a Pool?
The most common method used to heat swimming pools is through a solar thermal collector. A thermal collector absorbs and transfers heat from the sun to a heating fluid that then heats the water in a swimming pool.
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How do solar panels heat a pool?
Water comes into the system and is pushed to the collector where it is heated before being circulated back to the pool. Aside from the solar thermal collector, a solar water heating system will have:
- A filter that cleans the water in the system.
- A pump that circulates water through the system.
- A flow control valve that diverts the water to the collector.
There are two main types of solar thermal collectors. These are glazed and unglazed collectors.
Glazed collectors
Glazed collectors are made with copper tubes over an aluminum plate and have a glaze or iron tempered glass cover. Glazed collectors are more efficient at heating water although the glazing does make them more expensive. Their higher efficiency makes them better suited for colder climates.
Glazed collector systems can also be fitted to heat water for use in your home.
Unglazed collectors
Unglazed collectors as you may have already guessed, do not have glazing. They are made of rubber or plastic. The cheaper parts and simpler design make an unglazed collector less expensive than a glazed collector system. Their reduced efficiency makes them more suited to indoor pools and warmer climates. (Source)
How Many Solar Panels Would It Take to Heat a Pool?
Sizing a swimming pool solar system depends mainly on pool size, climate, and the collector. A simple rule of thumb is to make the surface area of your collector 50 to 100% of the surface area of your swimming pool. The cooler your regional climate, the bigger the ratio. Some solar contractors recommend a 1-to-1 ratio.
Pool size
Naturally, the bigger your pool the larger the surface area that needs to be covered. This means more collectors. For a length-by-width pool, you simply multiply to get the surface area. For an irregularly shaped pool, you can use Google Maps to work it out.
Climate
Regional temperatures play a big role in sizing a solar system. States like Arizona or California, receive more sunlight and are hotter. If you’re in Washington or New York, for example, you will likely need a bigger system with glazed collectors to compensate for the cooler weather and fewer sun hours.
You can make do with a smaller, less efficient system if you live in a location with more peak sun hours and higher temperatures. (Source)
The collector
The most important things to get right about the collector are the siting, orientation, and tilt of the collector.
- Solar panels need to be located in direct sunlight and away from shade.
- They should be orientated toward the true south or 45° east or west of south.
- They also need to be tilted at an angle that’s 10° more or less than your latitude depending on the time of the year. If you are mounting them on your roof, you can get away with mounting them flat if your roof is already sloped.
These are the main factors that account for solar pool heating system sizing. You might also want to consider how warm you want the water to be and how long the swimming season is. If you have warm months for most of the year, you would probably want a smaller system.
How Many Solar Panels Does It Take to Power a Pool Pump?
You need between 1,000 to 1,500 watts or four to six 250-watt solar panels to power a 1 ½ to 2 horsepower pump. To work out the exact number you need for a pool pump, you need to know the pool pump’s consumption and how much solar energy you receive in your location.
Pool pump consumption
A 1 ½ to 2 horsepower pump uses between 1.8 to 2.4 kilowatts per hour. Running it for 8 hours consumes up to 19.2 kilowatts. Pool pump consumption is measured in horsepower (HP). 1 HP is 745.7 watts per hour.
Available solar energy
How much solar energy you get is a factor of your location. Depending on where you are you will either have fewer or more peak sun hours from which your solar panels can produce energy to power your pump. Warmer states that receive more sunlight require fewer solar panels than cooler states. Find out how much sun your home receives here. (Source)
| Pump size | Daily Consumption (8 hours) | Solar panels required (250 Watt) |
| 0.5HP | 2.982 kWh | 2 |
| 1HP | 5.965 kWh | 4 |
| 1.5HP | 8.95 kWh | 6 |
| 2HP | 11.9 kWh | 8 |
| 2.5HP | 14.9 kWh | 10 |
For more details on this topic, we highly recommend that you check out our post “What Size Solar Panel To Use For A Well Pump? All You Need to Know!
How Long Does It Take to Heat a Pool with Solar Panels?
Heating a pool with solar panels takes between three days to a week. It depends largely on your system and your location. A glazed system will heat your pool quicker than an unglazed collector system. A pool in California will heat up quicker than a pool in New York.
The reason for the differences is that the starting temperature for a pool in California is much higher since the regional climate is warmer. There is also more sunshine from which the solar panels draw heat.
Are Solar Panel Pool Heating Systems Worth It?
The main advantage of using solar for heating or pool pumps is the cost. It’s much cheaper to run your pool on solar than it is through gas or electricity. Although the upfront cost is higher, the system more than pays for itself within 3 to 8 years of purchase.