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Solar Pool Heating System Overview

Solar swimming pool heating is the most cost-effective use of solar energy in many climates.

You can significantly reduce swimming pool heating costs by installing a solar pool heater. They’re cost-competitive with both gas and heat pump pool heaters, and they have very low annual operating costs. Actually, solar pool heating is the most cost-effective use of solar energy in many climates.

How a Solar Pool Heating System Works

Most solar pool heating systems include the following:

  • Solar collector — The device through which pool water is circulated to be heated by the sun
  • Filter — Removes debris before water is pumped through the collector
  • Pump — Circulates water through the filter and collector and back to the pool
  • Flow control valve — Automatic or manual device that diverts pool water through the solar collector
a diagram of a solar pool heating system

Example of a solar pool heating system.

Swimming pool water is pushed through by a solar pool pump through the filter and then through the solar collector(s), where it is heated before it is returned to the pool. In hot climates, the solar thermal collector(s) can also be used to cool the pool during peak summer months by circulating the water through the collector(s) at night, where heat can be radiated to the relatively cool night air.

Some systems include sensors and an automatic or manual valve to divert water through the collector(s) when the collector temperature is sufficiently greater than the pool temperature. When the solar collector temperature is similar to the pool temperature, filtered water simply bypasses the collector(s) and is returned to the pool.

Solar pool collectors can be made from different materials. The type you’ll need depends on your climate and how you intend to use the collector. If you’ll only be using your pool when temperatures are above freezing, then you’ll probably only need an unglazed collector system. Unglazed collectors don’t include a glass covering (glazing). They are generally made of heavy-duty rubber or plastic treated with an ultraviolet (UV) light inhibitor to extend the life of the collectors.

Because of their inexpensive parts and simple design, unglazed collectors are usually less expensive than glazed collectors. These unglazed systems can even work for indoor pools in cold climates if the system is designed to drain back to the pool when not in use. (It is extremely important not to leave any water in the collectors when the temperature might reach freezing.) Even if you have to shut the system down during cold weather, unglazed collectors may be more cost-effective than installing a more expensive glazed collector system.

diagram of a solar collector for solar pool heating

Glazed solar collector systems are generally made of copper tubing in an insulated aluminum framework with a low-iron tempered glass covering, which increases their cost. In colder weather, glazed collector systems—with heat exchangers and transfer fluids—capture solar heat more efficiently than unglazed systems. Therefore, they can be used year-round in many climates. Glazed collectors also can be used to heat domestic (household) hot water year-round.

Both glazed and unglazed collector systems should include freeze protection if they’ll be used in colder conditions. For unglazed systems, freeze protection will be a matter of proper plumbing to assure complete drainage of water from the collectors and piping; for glazed systems used year-round, freeze protection will focus on the correct ratio of antifreeze-to-water (non-toxic, food-grade propylene glycol is normally used) in the transfer fluid, to safeguard against freezing.

How Much Does a Solar Pool Heating System Cost?

A solar pool heating system can cost between $1,500 (unglazed) and $10,000 or more (glazed) to buy and install, depending on system type and pool size. Payback period will depend on your local fuel costs, but periods between 1.5 and 7 years are not uncommon. The solar collectors also typically last longer than gas and heat pump pool heaters. Your actual cost and payback depend on many factors. Therefore, before you purchase and install a solar pool heating system, you should do the following:

  • Evaluate your site’s solar resource
  • Determine the correct system size
  • Determine the system’s efficiency
  • Compare system costs
  • Investigate local codes, covenants, and regulations

Solar Pool Heating System Installation and Maintenance

The proper installation of a solar pool heating system depends on many factors. These factors include solar resource, climate, local building code requirements, and safety issues. After installation, properly maintaining your system will keep it running smoothly for 10–20 years. Consult your contractor and read your owner’s manual for maintenance requirements. Your collector should require little maintenance if the pool’s chemical balance and filtering system are maintained regularly. Glazed collectors may need to be cleaned in dry climates where rainwater doesn’t provide a natural rinse.

Source: U.S. Department of Energy’s Office of Energy Efficiency and Renewable Energy