Swimming Pool Solar Heating

Solar pool heating is one of the most economically attractive solar technologies in use today. If you are interested in heating your pool, or can no longer afford heating it with fossil fuel alone, consider installing a new solar pool heating system. We are a licensed solar contractor with fair prices, a quality product, and we do a professional job on installation.

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Determining the cost of pool heating is very site-specific, with many variables to consider. A solar pool heating system has a typical payback period of between 2-4 years. There are several factors that affect the savings realized with a solar pool heating system, including the size of the pool, your cost for natural gas, the pool temperature you wish to maintain, whether you use a pool cover, the length of your swimming season, the climate zone, etc. A utility company study monitoring the amount of energy to heat a 500 sq. ft. pool in Santa Clara California, from May through September, at a constant 80 F used approximately 1200 therms of natural gas. For residential summertime tiered gas rates this would approach $1,200 per year. For the same pool, a 400 sq. ft. solar pool heating system would maintain the same or higher temperatures through the same swim season and extend the season. A typical solar pool heating system of this size has an average installed cost of approximately $6,500, depending on location and placement of the panels.

(The figures below vary and do not include labor, plumbing, or automation).

This system easily achieved a 4-year payback...

• GAS POOL HEATER Initial Cost: $3,600.00
• 5-Year Operating Cost: $15,000.00
• Total Cost Over 5 Years: $18,600.00
• SOLAR POOL HEATER Initial Cost: $7,500.00
• 5-Year Operating Cost: $0.00!
• Total Cost Over 5 Years: $7,500.00
• That’s a savings of $11,100.00...and free heat from the sun makes pools enjoyable!

The following information helps answer the most frequently asked questions concerning solar pool heating. Keep in mind that much of this information is a "rule of thumb". Your individual situation, if analyzed in detail, may differ somewhat from the general application. A more detailed analysis of your pool system and the possibility of installing a new solar system can be provided to you as a complimentary service. Contact us and we will come and give you our honest professional opinion.

Q: What does it cost to heat a pool with a standard fossil fuel heater?

A: There are approximately 800,000 swimming pools (including above-ground) in California, and most of them must be heated during the cooler months to maintain comfortable swimming conditions. An unheated pool will stay generally at about the average outdoor temperature, which may be as low as 30°- 53°F in winter. For the typical user, comfortable pool water temperatures are 78°F to 82°F in spring and fall and 76°F to 78°F in winter. Average yearly cost for heating a residential pool is based on many factors, too many to mention here. Some the main factors are a cover, the pool size, the outside temperature, the size and efficiency of the heater and so on. The cost of using solar energy after the initial purchase is very minimal. The only operating expense when using solar is the price of running the filter pump. With today's new energy efficient high flow variable speed pumps, it is 50% less than it was just years ago.

Q: How does solar compare with other forms of pool heating?

A: A typical solar heating system costs from $4,500 to $8,500 installed. Compared with average fossil fuel heating, a solar pool heater offers a most favorable payback of 1.5 to 7 years. In addition, the solar pool heating industry is mature. It has numerous distributors and contractors and a track-record of over 20 years of experience. While in operation, the solar system is proving a supply of free heat. Over a 15 year period, there is a lot of expense saved in heating costs. Please note that the actual cost of solar pool heating systems depends upon many factors — ease of installation, type of financing, location of pool in north or south, length of pool season desired and building code requirements. These variables cause price variations and the homeowner should talk to more than one dealer-installer when considering a purchase.

Q: How does a solar pool heater work?

A: Imagine a garden hose that has been lying in the sun. When you turn on the faucet, out comes hot water. That’s solar heating. The sun’s energy has been absorbed by the hose and transmitted as heat to the water inside it. The hose acts as a solar collector. Comfortable swimming water temperature is relatively low compared to other uses of hot water. This allows the use of simple, efficient solar collectors (see following question). These systems require no separate storage tank, since the pool itself serves as the storage tank. In most cases, the pool’s filtration pump is used to force the pool water through the solar panels. In some retrofit applications, a larger pump may be required to handle the needs of the solar system, or a small pump may be added to boost the pool water up to the solar collectors. When adequate sunshine is available, the filtered pool water is circulated through the solar collectors, where it is heated by solar radiation and then returned to the pool. In this operation, the water goes from pool to pump, from pump to filter, from filter to collectors, from collectors to fossil-fueled backup heater (if there is one), from fossil-fueled heater to automatic chlorinator (if there is one), then back to the pool. Automatic controls may be used to direct the flow of filtered water to the collectors when solar heat is available. This may be accomplished manually by the use of a manual "bypass" valve placed in location P of Figure 1. Normally solar systems are designed to drain down into the pool when the pump is turned off. This provides the collectors with freeze protection. In central or southern states, water is sometimes circulated through collectors at night in summer to lose heat if the pool become too warm.

Q: What are the general types of swimming pool collectors used?

A: At the present time, the solar industry is almost exclusively using black polypropylene plastic collectors. These panels may be either rigid or have individual pipes running lengthwise. Individual collectors are normally 4'x8'; or 4’x10' or 4’x12', depending on the roof space or installation variables. Other types of pool collectors are flexible rubber mat, arrays of black plastic pipe or tube-on-sheet panels made of copper or aluminum. Glass covered or glazed collectors, commonly used for domestic water heating, are not as cost effective for pool heating as unglazed collectors and are not used for pool heating, due to their likely corrossion and excessive costs.

Q: How do the different types of collectors vary in performance?

A: The performance of pool heating collectors does not vary significantly when comparing their energy delivered per day per square-foot of equivalent collector area (i.e., Btu/day-sq ft). Thermal performance ratings for all collector types are available from the Florida Solar Energy Center Public Information Office. (Request publication FSEC-GP-16.)

Q: How long will solar pool heaters last?

A: Most plastic collectors manufactured for swimming pool use contain ultraviolet screening materials called inhibitors. The actual mix of the inhibitors is generally a manufacturer’s secret; but properly protected collectors should last 10 to 15 years.

Q: What is the proper orientation and tilt of the collector panels?

A: Ideally, solar collectors should face south. However, an orientation of up to 45° east or west of due south will not significantly decrease performance as long as shading is avoided. For optimum pool heating in winter, solar collectors should be tilted at latitude plus 15°. However, in California they are almost always mounted directly to the sloping roof. Standoff mounting to optimum tilt from a sloped roof usually will increase performance only 2 to 8 percent and is hardly worth the effort.

Q: Can I use one solar system to heat both my pool and domestic water supply?

A: No. Swimming pool heaters do not have covers (glazing) and are designed to heat a large volume of water (thousands of gallons) to relatively low temperatures (around 80°F), while hot water systems raise less than a hundred gallons to about 130°F. The energy used to heat 100 gallons of water to 130°F daily is a drop in the proverbial bucket compared to that needed to heat a pool. To do so, a similar collector area of glazed hot water-type collectors would be needed; but the additional cost of the higher temperature collectors would be unnecessary. In fact, pool heating collectors are generally more efficient at low temperature than the hot water type.

Q: Can I install a solar pool heater myself?

A: Generally speaking, yes. But only a person who is very handy at plumbing and electrical wiring should consider installing a solar pool heating system. The first time around, you and a friend can expect to spend two days putting in a system that would take an experienced crew six hours. This is hard work on a hot roof; but you can usually save at least one-third of what you would otherwise pay a solar contractor for the installed system. If you plan to install your own system, thoroughly read the manufacturer’s installation manual. Most collector manufacturers have an installation video in addition to the installation manual. View it carefully.

Q: How can I find a solar pool heating installer - contractor?

Q: How do I go about choosing a solar installer - contractor?

A: As with any purchase be sure to ask about a contractor’s experience, the collector warranty and maintenance. It is also a good idea to ask more than one contractor for a cost estimate. When comparing different contractors the most important item to compare is the amount of collector area specified by each contractor.

Q: How big of a collector system do I need?

A: Heating a swimming pool requires a large amount of energy. As a result, a large collector area (typically 350-500 square feet) is necessary to collect the solar energy needed, regardless of the type of collector used. Thus, from 7 to 12 black plastic panels will be required for typical residential pools. The collector area is usually about the same size as the pool surface area in northern California, about 80 percent of the pool area in central California and about 65 percent in southern California; but these numbers may vary significantly depending on the requirements of the pool.

Q: What about solar panel maintenance?

A: A properly installed solar pool heating system should require very little or no maintenance. However, regular maintenance of the pool and its filtration system is crucial. Pool pH and chlorine levels must be maintained within the limits specified by the pool water test kits. Chemicals should be added to the pool water far from the collector intake pipes. The filter should be cleaned as frequently as recommended by the manufacturer to ensure that adequate flow is supplied to the collectors. Check the solar heating system for proper operation at the beginning of each swimming season, particularly if it has an automatic control. Remember, a properly operating solar collector feels cool to the touch. The temperature rise of the water going through the collectors should be from 3°F to 5°F for most efficient operation.

Q: What about pool covers?

A: The greatest loss of heat from a pool occurs from its surface because of evaporation. By reducing this evaporation loss, pool covers are very effective in lengthening the swimming season. They also keep the pool clean, thereby lowering the cost of chemicals and filter maintenance. Depending on materials and the number of hours of use, temperature increases of 5°F to 10°F may be expected from a pool cover. A 5°F increase is reasonable when the cover is used 12 hours a day; 10°F when it is used 20 hours a day. Transparent or lightly translucent covers work best because they allow solar energy to pass through and be absorbed by the pool water, and they also prevent heat loss at night. Opaque covers are best at night to prevent heat loss. A roller is a good investment to help you move the cover on and off the pool. Motorized rollers are also available. Pool covers will last from three to five years, depending on care in handling and storage. Nevertheless, they are your best buy for an extended swimming season. From the standpoint of energy conservation, a pool cover should always be used if / or whenever possible.

Q: Where can I get more info?

A: We will be happy to look at your pool, and inspect your roof, and perform a complimentary professional consultation at no charge. If you would like more information regarding a solar system, please contact us.