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Pool Heating

Heating a swimming pool can be very expensive. Since we receive the most solar radiation during the long days of summer when we use our pools, solar pool heat is a great idea.

All pools should have a solar blanket on top when not in use. It will reduce the amount of chemicals needed, cut evaporation, and raise the pool temperature about 10°. It is especially important to have the cover on at night when outside temperatures drop. We also suggest running the pump in the day rather than mixing up the water at night when heat loss is greater.   Home Power has a great article on their web site regarding pool energy use, from heating options to better variable speed lower energy pumps.  

There are special considerations with corrosion and salt water pools with solar thermal. So let us know if you have a saltwater pool.

solar pool heatingInstalling solar equipment for pool heat only is not currently eligible for most solar incentives.  But if you install a domestic hot water system you can send excess summer heat to your pool.  The additional cost to reach the pool, over a standard heat dump, is small and is not eligible for solar rebates but the majority of the system would be eligible if installed as part of the initial system.

There are 2 options for solar pool heat, stand alone systems, or using a domestic solar thermal system and a heat exchanger.  

Another option is allowing your boiler to provide pool heat, since it is idle in the summer. This works with well high efficiency modulating condensing boiler since their energy use is much lower than pool heaters. Your pool needs to be located reasonably close to the house and boiler to avoid a long plumbing run.  You will also need a stainless steel heat exchanger as pool water can be corrosive. 

If you are going to install a stand alone pool heater we strongly recommend one that uses heat pump technology and runs on electricity rather than propane.  The operational cost is far below propane and equal to natural gas and the purchase cost is about the same.  Plus, if you add solar electric panels you can offset the additional electric costs and allow the sun to heat your pool for free.

Solar Pool Heat Options for Above-Ground Pools

The key consideration in solar pool heat is are you looking to provide supplemental heat to improve comfort or do you want a system capable of truly heating the pool in May?  Supplemental systems can be quite affordable while taking a pool from 40 degrees to 80 requires a much larger, and more expensive, system.   

solar pool heat

  • DIY project. Get 200 ft of black 2 inch pipe. Connect it to the pool filter outflow. Place the pipe in the sun. Use a timer so you allow water to flow only when the sun is on the pipe. There are also temperature sensor to automatically divert the flow.  We have tested this and it did help raise the pool temp but to make a larger impact on a 24 ft round above ground pool required about $300 worth of pipe and at that point an inexpensive stand alone mat heater would be a better ROI.  Our test site was a west facing roof, not south.
  • Install a stand alone solar pool heater. These run about $250-750. You can buy a simple system on-line, or we are happy to install a higher quality system for you. Basically these are black “plastic” panels that the water is routed through. Ideally they are mounted on the roof, out of the way, where they can take advantage of radiant heat from the surrounding shingles.   You can expect these mats to last up to 10 years. 
  • If you have a Solar Thermal system that provides your home's hot water or heating needs, you probably find you have excess heat in the summer. With the use of a heat exchanger you can direct this excess to heat your pool water. Depending on location and pipe distance, the extra cost is about $2,400. This option will give the best performance and durability. While pool heating does not qualify for federal tax credits, most of the cost of using your pool as the necessary heat dump for your domestic solar thermal hot water system can if it is installed as part of the initial system.
  • A non-solar option, if you have a good modulating condensing boiler, is to add a pool heat exchanger and let the efficiency boiler heat the pool.  Most pool heaters are <80% efficient and a good boiler is > 90.   This is only practical if you can get a plumbing line from the pool to the boiler.  You will need a stainless steel pool heat exchanger to keep the pool water separate from the boiler loop.

Solar Thermal Pool Heating Options for In-Ground Pools

Generally speaking, an in-ground pool contains much more water than an above-ground pool and the surrounding soil provides better insulation. A in-ground pool can use any of the above options, but due to the increase amount of water, the system sizing will increase. If you have an in-ground pool we highly recommend you consider installing solar thermal for your domestic hot water needs and use your pool as a heat dump. While pool heating alone does not qualify for federal tax credits, most of the cost of using your pool as the necessary heat dump for your solar thermal domestic hot water system can if it is installed as part of the initial system.

For commercial applications, such as camps or summer-only hotels we recommend flat plate solar thermal collectors. They give excellent spring/fall output and are less expensive than evacuated tubes. They can provide hot water for shower facilities as well as the pool.

Solar Heating Options for Hot Tubs

Hot tubs have small quantities of water, but the temperature needs to be high. The inexpensive solar mat type heaters will not create the temperatures necessary. You can use your hot tub as a heat dump (see above) for your solar thermal domestic hot water/heating system. Due to the tub's small size, it is likely that you will still need an additional heat dump to prevent overheating. Since hot tubs require careful temperature control, a backup system will still need to be in place. We find the majority of the time connecting to a free standing hot tub is not worth the additional expense.  See below for information on heat pumps that can also be used for hot tubs. 

Solar and poolIntegrating domestic solar thermal hot water with pool heating

Installing solar to meet your domestic hot water needs or space heating is popular.  Due to the long days in the summer these systems often produce more hot water than is routinely consumed.  Using the pool as a "heat dump" when the storage tank is satisfied is a practical choice to extend your swimming season and make the pool more comfortable.  Pool water can't mix with domestic water and can be corrosive so it is necessary to use a stainless steel heat exchanger that is designed for pool application.  Plumbing lines will need to be run from the pool to the solar pump station.  If there is any possibility that the pool will not be able to absorb all excess heat from the collectors, an additional heat dump should be installed. This may be the case when the pool is open for only a short period during the summer, especially with large solar thermal systems designed to do home heating.  

A new option: Heat pump pool heaters with PVRheem Pool Spa 6350 Heat Pump

Heat pumps for space heating and domestic hot water have become the hottest selling mechanical systems we have ever seen for good reason.  They are super energy efficient so they simply cost much less to operate than other source of heat.   Now we are seeing heat pump pool heater.   Just like other heat pumps these use electricity.  Heat pumps move heat they do not create it.  For every unit of electricity these heaters uses they will move 4-6 units of heat.  When you combine an electric heat pump with solar electric modules you let the sun provide the energy to heat your pool for free.  


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