Variable-Speed Pumps for Residential Swimming Pools
Residential Swimming Pool and Spa Pumps: Variable Speed vs. Single-Speed
Swimming pool and spa pumps with variable-speed control instead of a two or single-speed motor-driven pump.
Item ID: 37
Process Loads & Appliances--Commercial and Residential Appliances
Variable-speed or two-speed pool pumps are a cost-effective retrofit for old, single-speed pool filtration pumps. The 2009 Washington State Energy Code requires that new pumps of 1 hp or more be capable of operating at two or more speeds, but adoption of this technology is still low.
Retrofit energy savings depend on pump oversizing, whether the existing pool is open for the length of a swimming season and whether it has a single- or two-speed pump. A pump should be sized to turn the pool volume over at least once every 24 hours. If an existing single-speed pump achieved this turnover rate while operating continuously, the variable-speed pump would offer little in energy savings because it must provide the same flow rate. Some single-speed pumps are oversized and may turn the volume over in six hours. A variable speed pump would achieve the same filtration while operating with a reduced flow rate resulting in less energy consumption due to reduced pipe friction losses. Variable-speed control can also take advantage of time-of-day rates. Clogged drains, intakes or filters significantly reduce savings.
A variable-speed pool pump that replaces a typically oversized, single-speed pump could reduce energy use by 50% to 75%. Many swimming pool pump manufacturers use high-efficiency electronically commutated permanent magnet pump drive motors. A two-speed pump installation generally costs between $700 and $1,000, while installation of a variable speed pump, complete with controller and programmable task manager, typically costs between $1,400 and $1,800. Either alternative is superior to a single-speed pool pump. Several utilities provide incentives for replacing single-speed pumps with two-speed or variable speed pool pumps.
Baseline Description: Constant-Speed Pumps for Residential Swimming Pools
Baseline Energy Use: 2250 kWh per year per unit
The baseline is a 1-hp, single-speed pump operating continuously on a seasonal basis. Depending on the climate, it could be larger and could operate less of the time. New pumps 1 hp and over (at least in California) need to be 2-speed, but existing pumps could well be 1-speed. The 2014 Pennsylvania "Technical Reference Manual" notes that single speed pool pumps tend to operate well into their service factor---thus a 1 hp pump typically is loaded to provide 1.28 brake horsepower. The average pump motor efficiency is 70% (Pennsylvania PUC, 2014). Given 4 months of constant operation per year, a 128% load on the motor, and an average pool pump motor efficiency of 70% at that load point: the annual energy consumption is: 1 hp x 0.1.28/0.70 x 0.746 kW/hp x 2920 hours/year = 3,983 kWh/year.
Many pumps, however, operate with time clock control. E-Source indicates that residential pool pumps are massive "energy hogs" consuming an estimated 2,000 to 2,500 kWh on average each year (E-Source, 20 Technologies and Trends of 2013). An annual energy use of 2,250 kWh/year will be assumed.
Manufacturer's Energy Savings Claims:
Currently no data available.
Best Estimate of Energy Savings:
"Typical" Savings: 50%
Energy Savings Reliability: 3 - Limited Assessment
E-Source (in 20 Technologies and Trends of 2013) indicates that pool pump energy consumption can be reduced by 32 to 72%, largely through the use of variable-speed technology.
PG&E cites the example of a single-speed 3/4 hp pool pump with an input power of 1.2 kW when providing a flow rate of 60 gpm that runs for 6.9 hours per day while using 3,042 kWh/year. A variable pump would provide the same turnover while requiring only 0.18 kW when running at 33 gpm for 12.6 hours per day, using only 830 kWh annually for an energy savings of about 72%.
Energy Use of Emerging Technology:
1,125 kWh per unit per year
Energy Use of an Emerging Technology is based upon the following algorithm.
Baseline Energy Use - (Baseline Energy Use * Best Estimate of Energy Savings (either Typical savings OR the high range of savings.))
Potential number of units replaced by this technology:
The NEEA "Residential Building Stock Assessment: Multifamily Characteristics and Energy Use" indicates that 28% of multi-family buildings have a pool (Page 61). About 85% are outside and can be expected to operate seasonally. The remaining 10% are interior and are expected to operate year around. The interior pools are associated with assisted living and senior housing, but also tend to serve as amenities at higher-end apartments. The study also indicates that there are 543,730 multi-family customers in the Northwest (Baylon, 2013) (Page 9). The number of multi-family pools in the region is thus estimated at:
543,730 x 0.28 = 152,244
A paper presented at the RESNET 2013 conference (Easley, "Swimming Pool Energy Audits: Energy Savings for Homes with Pools) contains a listing of inground swimming pools by state. A total of 97,360 inground pools are estimated for the four Northwest states. It is thus estimated that a total of 249,604 residential type pools are in operation in the Northwest. We do not know how many are already equipped with variable speed drives (so assume "0").
It will be assumed that all of these pools are equipped with constant speed motors that run continuously during a four-month operating season.
Regional Technical Potential:
0.28 TWh per year
Regional Technical Potential of an Emerging Technology is calculated as follows:
Baseline Energy Use * Estimate of Energy Savings (either Typical savings OR the high range of savings) * Technical Potential (potential number of units replaced by the Emerging Technology)
Currently no data available.
Simple payback, new construction (years): N/A
Simple payback, retrofit (years): N/A
Cost Effectiveness is calculated using baseline energy use, best estimate of typical energy savings, and first cost. It does not account for factors such as impacts on O&M costs (which could be significant if product life is greatly extended) or savings of non-electric fuels such as natural gas. Actual overall cost effectiveness could be significantly different based on these other factors.