Solar Pool Heater Sizing

Proper sizing a solar pool heater is important to ensure you get the results you are looking for when investing in a solar pool heater. There are many variables that play an important part of a pool's heat loss requirements. In most pools 80-90% of the heat is lost through the surface of the pool. In ground pools are more insulated on the sides than above ground pools and the earth acts as a natural insulator. Because of the surface heat loss we always recommend the first investment should be a solar pool cover. Investing in a solar heater without a cover on the pool is like trying to heat a house when all the windows are open.
Wind speed and shading also play an important role in determining how much heat is lots from a pool. The windier the location the more heat will be stripped from the pools surface. Again a great reason to add a solar cover.

Solar insolation map

The outdoor temperature and season of use are also very important in determining if a solar pool heater will meet your expectations. If you are trying to heat an outdoor pool in Minnesota, you may extend your season to May- September. However in southern USA, a solar pool heater may allow you to comfortably enjoy your pool year round. Using a solar insolation map will be helpful in determining how much annual sun you can harness with your solar pool heater.

In some cases to meet your temperature objectives you may consider going with both a solar pool heater as well as a backup natural gas or propane pool heater. In this way you can rapidly bring up the water temperature in the spring and then allow your solar water heater with solar cover to maintain the temperature with little need for the gas pool heater.

Solar Vacuum Tube Pool Heaters will deliver substantially more heat to pools in colder climates. However in warm climates where pool temperatures exceed 90 F in the summer, the solar pool heating system may need to be covered up to avoid over heating the pool!
When calculating the number of vacuum tube collectors that are needed for a pool you can use the chart below as a general rule of thumb. However as mentioned many variable will play in determining how much energy is going into the pool versus how much is leaving. Only when there is a surplus of energy will the pool temperature rise.

Solar Pool Heating System Sizing*

Surface Area


100-200 ft2

200-300 ft2

300-400 ft2

400-500 ft2

SPH-1  X
SPH-2  X
SPH-3  X
SPH-4  X
SPH-5  X

 *NOTE Pools larger than this should use multiple pool heaters a 1000ft2 pool should use 2 x SPH-5 systems in parallel. Sizes are approximate, geographical location and the use of a pool cover will effect sizing.