Portable electric spas are self-contained hot tubs which are electrically heated. The most popular portable spas hold between 210 and 380 gallons of water; however, some models can hold as much as 500 gallons. “In-ground” spas are not included in this standard.
In December 2004, the California Energy Commission (CEC) adopted a maximum standby energy consumption standard of 5*(V2/3) Watts for portable electric spas where V = the total spa volume in gallons and 2/3 means to the two-thirds power. Standby energy consumption represents the majority (75%) of the energy used by electric spas and refers to consumption after the unit has been initially brought up to a stable temperature at the start of the season and when it is not being operated by the user. A maximum standby energy indexed to total spa surface area requires spas of all sizes to be equally efficient. In 2007 this same standard was adopted by Connecticut and Oregon. Arizona and Washington have also followed suit, both having adopted this standard in 2009, effective January 1, 2012 and January 1, 2010, respectively.
The American Pool and Spa Association (APSP) and a coalition of stakeholders developed updated standards for spas. The Standards were approved by the American National Standards Institute (ANSI) in September, 2014. The standard sets a maximum standby energy consumption level based on the size of the spa and requires spa labeling. A CEC rulemaking updating spa standards is expected to closely align with APSP standards.
Over half the energy consumed by a typical electric spa is used for its heating system. Heat is lost directly during use and through the cover and shell during standby mode. Improved covers and increased insulation levels are key measures to improving efficiency and can decrease standby energy use by up to 30% for a spa of average to low efficiency. Another measure is the addition of a low-wattage circulation pump or improvements to pump efficiency that would generally save 15% of standby energy consumption of an average-efficiency spa. Automated programmable controls, which would allow users to customize settings based on predicted usage patterns, are a third measure to improve efficiency and could save roughly 5% of a spa’s standby energy consumption. The California standard was a modest initial effort estimated to have been met by 80% of products in 2007. The market share has most likely increased as the standards have not been adjusted since 2004. The payback period varies considerably with regional temperatures and energy prices. For example, in New England states, with cold winters and higher than average energy prices, the payback is shorter than In warmer climates with lower energy costs.