Solar Pool Heater

A solar pool heater uses solar energy to heat water for a swimming pool. A solar pool heating system usually consists of solar collectors that absorb the Sun's energy. Water flows from the swimming pool, heats up as it flows through the collector, and then returns to the swimming pool. Solar swimming pool heaters are most effective when the Sun is shining, typically in warm, sunny climates. However, theycan extend the swimming season by a few weeks, even in cooler temperatures. This article covers how solar pool heaters operate, the different types of heaters, how to select and install them, and the advantages of using one.

Table of contents

• Working principle
• Solar pool heater types
• Selecting the right solar pool heater
• Solar pool heater installation
• Advantages
• FAQs

Working principle

A solar pool heater typically uses plates to heat pool water before it gets pumped into the pool. Pool heater plates have the following components:

• Solar collectors: Solar collectors are the actual heating plates installed on the roof (Figure 1) or a rack near the pool. Collectors are made of metal tubes, called riser tubes, coated with a black absorber that absorbs the sun's energy. Water enters at the bottom of the heating plate and moves up the riser tubes as it heats up. The outlet is at the top of the heating plate. Solar collectors are composed of different materials. The type of collectors needed will depend on the climate and how the collector is used.
• Pump: The pump pushes the water into the solar collectors for heating and returns the heated water to the pool, raising the overall temperature of the pool. The electric grid can power the pump, or it can be a solar pump with dedicated solar panels to provide power.
• Filter: The filter removes debris and contaminants from the water to keep the system clean.
• Control system: The control system monitors the temperature of the water in the pool and the temperature of the water coming out of the solar collectors. If the water in the solar collectors is warmer than in the pool, the control system will turn on the pump to circulate the water through the solar collectors and back into the pool.
• Valves: An automatic control valve between the filter and the return line to the swimming pool opens fully to bypass the solar heater when heating is unnecessary. It can also be partially opened to limit the amount of water going into the solar heater and thus limit the pressure. A check valve between the filter outlet and solar heater inlet prevents backflow from the solar heater. A check valve at the solar heater outlet prevents cold water from entering the hot water piping. Learn more by reading our article about valves used in swimming pools.
• Safety features: Solar pool heaters are equipped with safety features to prevent overheating and protect the system from damage. These may include temperature and pressure relief valves and automatic shut-off valves.

Solar heating types

In general, there are three types of solar heating plates: solid-body, separated tube, and glazed. This section describes each type of heating plate and then discusses their pros and cons.

Solid-body heating plates

Solid-body heating plates have riser tubes that all combine directly together or are combined with thin strips of cloth. Due to no open space between adjacent riser tubes, these heating plates are ideal for windy climates. There is less surface area for the wind to remove heat via convection. However, this type of heating plate has thinner riser tubes, making it more vulnerable to freezing damage if not properly winterized. To winterize, turn off the solar heater’s circulation system (e.g. pump) and allow water to drain from the collector. Then isolate the collector with a ball valve on the input side and a check valve on the return side. Finally, switch the control valve to bypass so the pool’s filter system can run without water going through the collector.

Separated tube heating plates

Separated tube design heating plates have riser tubes that do not join together. This design does allow wind to carry heat away from the heating plate. However, it is also more stable during extreme wind because wind can pass through the riser tubes. The most efficient use case for separated tube heating plates is a low-wind environment. Finally, separated riser tubes tend to be thicker and less susceptible to freezing damage. They still require proper winterization, however.

Glazed heating plates

Glazed heating plates have a separated tube design, but the risers are coated in an acrylic glaze. The acrylic glaze traps heat within the riser tubes that wind cannot easily carry away. Therefore, glazed heating plates are more efficient than other types of heating plates but have a higher price compared to other solar collectors. This efficiency is especially true in colder and windier climates.

Heating plate pros and cons

Heating plate type	Pros	Cons
Solid-body	Limit heat loss from wind Relatively easy to install Relatively low cost	Do not fit well on tile roofs Vulnerable to freezing damage Must be strapped down
Separated tube	Less vulnerable to freezing damage Less susceptible to being lifted by the wind	Heat loss in windy environments
Glazed	Provide warmer water in colder climates Typically have the best warranty	Most expensive

Selecting a solar pool heater setup

The cost of a solar heater for pool can be on the higher end. But, these systems are an excellent long-term investment. Here are a few factors to consider when selecting the right solar pool heater:

• Heating plate type: See the above section about different heating plates to help determine the best plate based on cost and environmental conditions.
• Total heating plate size: Multiple heating plates are typically necessary to heat a swimming pool effectively. The combined surface area of the heating plates should be 50%-100% of the pool's surface area. The optimal surface area depends on how long the pool will be used. For a few months of heating during the, summer, 50% is adequate. For heating as long as possible through the year (i.e., not the freezing months), 100% is necessary.
• Direct heating: The optimal total surface area of heating plates is also affected by how much direct sunlight reaches the pool. Discuss this with a solar heating plate professional before deciding on the number of plates to purchase.
• Pump type: As discussed above, conventional pumps and solar pumps are applicable for solar pool heater systems. If considering a solar pump, determine if enough sunlight is available to power the pump throughout the year. This can save on energy costs in the long run.

Solar pool heater installation

There are several factors to take into consideration when installing a solar heating system for a swimming pool. Due to variations in these factors, there is no universal installation method. Therefore, the best option is to hire a professional to ensure correct installation and long-lasting use. During installation, factors to consider include the following:

• Orientation: In the northern hemisphere, the heating plates should be on the roof's south- or southeast-facing side. The next best orientation is west, and then finally east. Do not install heating plates on a north-facing side of the roof. The opposite is true in the southern hemisphere: the best location is north- or northwest-facing and plates should not be installed on the south-facing side of the roof.
• Heating plate configuration: To ensure consistent flow rates, a single row of heating plates is the most common configuration (Figure 2). A double row or split feed configuration is desirable if the water source's flow rate exceeds the maximum allowance for the plates.
• Pump horsepower: A 1-horsepower pump is adequate for most solar pool heater configurations. In the case of a very high roof, long pipe run, or large number of heating plates, a higher horsepower pump may be necessary. If the pump’s horsepower is not high enough, the flow rate through the heating plates will be less than desirable.
• Plumbing: Due to its higher temperature resistance, CPVC pipe is necessary on the return side of the heating plates. PVC or CPVC is adequate for the supply side. Do not undersize the pipes. Depending on the required flow rate for the heating plates, adequate pipe diameters are:
  • 0 - 114 lpm (30 gpm): 38 mm (1.5 in)
  • 115 - 189 lpm (31 - 50 gpm): 50 mm (2 in)
  • 190 - 265 lpm (51 - 70 gpm): 64 mm (2.5 in)

Advantages

• Cost-effective: Solar energy is a renewable and free resource. So once the initial investment in the pool solar heater has been made, there are no ongoing energy costs.
• Environment-friendly: Solar pool heaters do not produce any greenhouse gasses, making them a more environmentally friendly option than gas or electric heaters.
• Extended pool heating: Solar pool heaters can extend the swimming season by heating water to a comfortable temperature even when the surrounding air is cool.
• Low maintenance: Solar pool heaters require minimal maintenance and can last many years with proper care.

Read our articles on portable, radiant floor, and electric infrared heaters for more details on various heater types.

FAQs

What is a solar pool heater?

A solar pool heater system uses solar collectors (heating plates) to heat water that circulates through the system and back to the pool.

Can an existing pool pump be used with a solar pool heater?

Yes, a solar pool heater works with an existing pool pump. Solar heaters only increase pool systems by a few pounds per square inch. As long as the pump isn't operating near its limits, there shouldn't be any problem.

Can you heat a pool with solar panels?

Solar panels for pool heating are part of a solar pool heating system. This system heats up a pool by using solar energy.