Solar swimming pool heaters rely entirely on the sun's energy to heat pool water. As water circulates through the solar panels, heat from the sun's rays is transferred into the water. While some solar swimming pool heaters are designed to be set up on rooftops or mounted on wooden racks, other models can be installed on the ground.
Pros and Cons of Solar Pool Heaters
- Low Initial Cost
- Zero Cost to Operate
- Ecofriendly, Zero Emissions
- Entirely Weather Dependent
- Lower Heat Gain
Solar pool heaters for pools are less expensive to buy than gas-fired heaters or pool heat pumps, but if you want to add 15-20 degrees F to the water, you need to use enough solar panels to equal at least 50% of the pool surface area. For most inground pools, a good solar system will cost $1500-$2000, still one of the cheapest methods of heating a pool. For most above ground pools, a good solar system will cost $250-$750, still one of the cheapest methods of heating a pool.
With no cost to operate the solar panels, other than the cost of running the filter pump, which you are may be doing anyway, solar pool heating is the least costly way to heat an inground pool.
In terms of environmental friendliness, solar pool heating is the clear leader. No fossil fuels, no emissions, no fuels or refrigerants needed, only the sun; a renewable resource. Solar panels, made entirely of thermoplastics, are also more easily recycled than other pool heater types.
The largest drawback to solar pool heaters is that they are entirely dependent on sunny weather. They can still heat the pool on warm and partly cloudy days, but with cool and rainy weather solar heaters lose heat, and they don’t work at all during the night.
Another disadvantage attributed to solar pool heaters is lower overall heat gain. However, solar systems are modular, and the more panels you have, the greater heat you can add to the water. If you have a sunny southern facing location to place enough panels to equal 50-80% of your pool surface water, and you get at 6-8 hours of daily unobstructed sun - you can match the heat output of a gas heater or heat pump, adding 20-30 degrees F to the pool. A small solar system however, or one with only 4-6 hours of daily unobstructed sun may only gain 5-10 degrees, which is easily lost with a few cloudy days.
What does the Ideal Solar Pool Heater System look like?
A southern facing single story roof that’s at least 20’ long, with unobstructed sun, for at least 6 hours daily would be best. Even better if it is close to the pool pump and filter, so that long plumbing runs aren’t required. Another good location would be a free standing, triangular shaped rack, built of slotted angle bracing or lumber framing with a plywood deck. These can be placed up against a fence, on the sunny side. Or a pergola or pool cabana can be used, if the roof has a 10' width.
How many solar panels are needed?
The more panels you have, the more heat you can harvest. Swimming pools in ideal solar conditions should use at least 50% of the pool surface area, For example, an 18x36’ pool has a surface area of 648 square feet. 50% of that would be 324 feet of solar panel surface area, or about 4 of the 4’x20’ panels, which are 80 sq ft each. In less than ideal conditions, such as an east/west orientation, or partial sun obstruction from trees or houses, a higher multiplier of 70-80% can be used, to compensate for panels that receive less direct continuous sun. Remember that the sun is always moving across the sky as our seasons change. A large tree that doesn’t block the sun during May could be a real shade tree in September. Also you need enough solar panel surface area to make a reasonable difference. An undersized solar system will only produce 5-10 degrees of heat.
Can solar panels be installed on separate roofs?
Yes, you can install separate sets of panels, in series, on different facing roof sections for instance. The water will run through the first panel set, exit and then enter the second set of panels.
Do I need a booster pump?
No, most solar systems operate just fine on the volume of water pushed from the existing filter pump. Even installing panels on a second story roof is no problem for most inground pool pumps. There are instances where a larger filter pump or booster pumps are recommended, but these are not the norm.
Installing a Solar Pool Heater System
Not too difficult to do, most in ground pool solar heaters can be installed in one day. Above ground solar heaters can be installed in less than an hour. Location is most important, so after figuring out if you will install on a roof, fence or deck, the panels can be installed. A southern orientation is best in the US, and installing at a 45 degree angle will absorb more heat. The solar panels can be roof mounted in a few hours, secured to protect them from winds. Then you connect plumbing from the return line, after the filter, to the panels on the roof, securing vertical pipes to the wall. The final step is usually wall mounting the solar controller and installing the temperature sensors.
Care and Maintenance of a Solar Pool Heating System
Solar heating systems require very little maintenance. It is important to keep your pool water balanced and your filter in good operating condition. Since the water that goes into the solar collector comes straight from the filter, if there is anything that bypasses the filter, it can potentially clog the solar collector.
Improper pH and calcium hardness can cause mineral build up in the solar collectors. Low pH or high levels of chlorine can cause the plastic to become brittle. If you have very high calcium hardness levels in your pool, use a scale inhibitor on a regular basis to prevent mineral build up in the solar collector.
Although rare, splits or damage to the tubes in a roof mounted solar pool heater can be repaired with an inserted plastic sleeve. This works similar to a stint placed in a blocked artery. One of the greatest things about solar pool heaters is their reliability, and simple design.
How long do solar pool heaters last?
Ironically, the summer sun will eventually attack a solar pool heater, causing it to become brittle and breakdown. Most polypropylene solar heater panels will last at least 10 years in the hottest parts of the country, and longer in the more temperate regions. More durable solar panels made of rubber can last 20 years or more before the material begins to weaken.
Winterizing a Solar Heating System
Most solar heating systems have drain plugs to allow the water to drain out of the panels. They are often installed at a slight tilting angle to facilitate drain down. For proper winterization, it’s a good idea to blow air through the collector to remove any trapped water in the panels or on top of a vertically mounted check valve. Winterizing is also a good opportunity to inspect the collector panel for damage and inspect the mountings; to be sure the solar panels are secure and ready for the winter.
Solar panels for pools are typically manually operated by turning a valve to direct water into the solar panels. When sunny conditions wane, you must remember to turn the solar panels off again, or the water will radiantly cool as it passes through the cold panels. To avoid this, and to enjoy the convenience of setting a desired temperature, solar pool heaters can be controlled with the installation of a Solar Controller. These automatically turn a valve to send water to the solar panels when sensors signal that solar heating conditions are good, and bypass the solar panels when conditions are poor, or when the pre-set temperature is reached.
Sizing a solar heater for pools is done by measuring your pool’s total surface area, by multiplying the length x width. Buy enough solar panels to equal 50-80% of your pool surface area. For example, a 20’x40’ pool would have 800 sq. ft. of surface area, and would require 400-650 sq. ft. of solar panel surface area, for best results. The more solar panels you add; the more heat you get. It’s a good idea to oversize solar pool heaters, for windy areas, uncovered pools, or to compensate for bad weather. For above ground pools, consider modular units like the SunCoil Solar Dome.
Installation of a pool solar heater involves placing the solar panels in an area of unobstructed sun, cutting the return line after the filter, and redirecting the water through the solar panels. Valves are used to direct the water to the panels, and also to bypass the panels. For best results, a solar controller can be mounted, with sensor and valve actuator connected, to maintain a consistent temperature more easily. Solar pool heater installation is much less complicated than other methods, and the only one that is truly DIY friendly and fully achievable by most pool owners.
Solar pool heaters require no maintenance and will typically last for 10 to 15 years, before ironically, the plastic degrades from the sun’s solar rays.
Solar heaters are powerfully fast heaters in direct summer sun, but lose effectiveness in cooler, off-season months, when the sun moves lower through the sky. As such, they are not appropriate for year round pool heating, with exception to far southern regions of North America. For most northern regions, properly sized solar heaters can maintain warm water from May-October.
