Find the exact size heater you need. Calculate your required BTUs for gas heaters and electric heat pumps based on your pool volume and climate.
Buying an undersized pool heater means your water will never get warm enough in the fall, and your energy bill will skyrocket because the unit never shuts off. Here is how to size it correctly:
Pool heaters are measured in BTUs (British Thermal Units). One BTU is the exact amount of energy required to raise the temperature of one pound of water by 1°F.
Because a single gallon of water weighs 8.34 pounds, a 15,000-gallon pool contains over 125,000 pounds of water. That is a massive thermal mass, which is why pool heaters are often the largest appliances on a residential property.
Gas heaters use combustion to blast heat directly into the water. They range from 150,000 to 400,000 BTUs. They are incredibly powerful and can heat a pool by 1°F to 2°F per hour, but they consume expensive natural gas or propane to do it.
Heat pumps don't generate heat; they extract ambient heat from the outside air and transfer it into the water. They top out around 140,000 BTUs, meaning they heat the pool very slowly. However, their monthly operating cost is incredibly low.
It depends on your lifestyle. If you only swim on weekends and want to heat the pool quickly on Friday afternoon, or if you have an attached spa that needs to hit 102°F fast, get a gas heater. If you want the pool to be a consistent 85°F all week long and you live in a relatively warm climate, get a heat pump to save on energy costs.
If you undersize your pool heater, it will run continuously trying to reach your target temperature. In colder shoulder months (like April or October), an undersized heater may completely fail to overcome the natural heat loss of the pool overnight, meaning the water will never reach your desired temperature.
Yes. Up to 75% of a swimming pool's heat loss occurs through surface evaporation. Using a powerful gas heater or heat pump without a solar cover is like running your home's air conditioning with all the windows wide open. A solar cover traps the heat overnight, cutting your heating bills by up to 50%.
Before you upgrade your heater, ensure your pump and filter are operating efficiently to provide adequate water flow to the new unit.