Pool heaters are used to heat the water contained in swimming pools, spas, and hot tubs. The water is heated as it passes through the pool heater, which is installed on the water line that circulates pool water through the filter. A thermostat turns on the heater when the water temperature is too low and shuts it off when the water reaches the desired temperature. Although there are several types of pool heaters, including those powered by gas, oil, electric resistance, heat pump, and solar energy, gas-fired heaters are the most widely used and offer good efficiency opportunities.
On April 16, 2010, DOE issued its final rule for gas-fired pool heaters, establishing new efficiency standards for the first time in over two decades. The new standard, effective April 2013, requires a minimum thermal efficiency of 82%. According to DOE, the standard will save .02 quads of energy over 30 years, save consumers about $40 million and reduce carbon dioxide emissions by 75 million metric tons. A national efficiency standard for gas-fired pool heaters was first established in 1987, requiring a minimal thermal efficiency of 78%. California and Connecticut have enacted regulations that prohibit constant-burning pilot lights in gas pool heaters.
In October 2015, DOE initiated a rulemaking to develop updated standards for pool heaters.
Pool heaters consume 7.6 billion kWh nationwide each year. Basic, inefficient pool heaters have a standing pilot, which can be replaced with electronic ignition to reduce gas consumption. The thermal efficiency can also be increased by adding additional heat exchange area relative to the current standard. Other possible efficiency improvements include: electronic ignition; power venting, where draft fans are installed around the combustion zone helping to regulate the amount of air at the burner to obtain higher combustion efficiency; sealed combustion, where combustion chambers are sealed to prevent excess air from impacting thermal efficiency, and; condensing, where water vapor from the combustion gases is condensed to capture the heat released during vaporization.