California case study
In October 2010, the upgrades described here were completed on a residential swimming pool in California in an attempt to reduce one pool’s energy consumption and its owner’s electricity bill.
California has a tiered electric utility rate structure, so the more kilowatt-hours used, the more a customer pays. It ranges from 12 to 40 cents per kWh, and swimming pools almost always correlate to the higher rate. Before the upgrades it cost $2,100 US per year to run the filtration, cleaner, light and solar heater on this 75,700-L (20,000-gal) pool. A separate waterfall pump also consumed energy, but was rarely used because it was loud and inefficient.
Before upgrades
- 1.5-horsepower (hp) standard pool pump (for filtration and solar heating);
- sweep-style pool cleaner with a ¾ hp booster pump;
- 2-hp waterfall pump; and
- 500-watt incandescent light
The original single-speed pump ran an average of six hours per day during the summer months, drawing about 2,100 watts for filtration and heating. The pool cleaner’s booster pump, which ran approximately 2.5 hours per day, drew an additional 1,400 watts. Combined, these two pumps were using an average of 16 kWh per day.
After upgrades
- variable-speed pump (for filtration, solar heating and pool cleaner);
- additional variable-speed pump for waterfall; and
- light-emitting diode (LED) lighting.
Filter pump upgrade
The main variable-speed pump draws 221 watts during the low-flow filtration cycle and 650 watts when it speeds up to operate the pool cleaner.
Filter pump operating cost comparison |
||||
|---|---|---|---|---|
| Function | Old pumps | New variable-speed pump | ||
| Summer | Winter | Summer | Winter | |
| Filtration | · 2,092 watts | · 2,092 watts | · 221 watts | · 221 watts |
| · six hours per day | · four hours per day | · six hours per day | · three hours per day | |
| · 12.6 kWh | · 8.4 kWh | · 1.3 kWh | · 0.66 kWh | |
| · $153 per month | · $102 per month | · $16 per month | · $8 per month | |
| Cleaner | (Year round) | (Year round) | ||
| · 1,372 watts | · 650 watts | |||
| · 2.5 hours per day | · three hours per day | |||
| · 3.4 kWh | · 2 kWh | |||
| · $42 per month | · $24 per month | |||
The cleaner’s booster pump used the same amount of energy year-round (3.4 kWh per day). When combined with the standard pool pump used for filtration and solar heating, this pool was consuming 16 kWh per day in the summer. The new variable-speed pump needs only 1.3 kWh per day for filtration and an additional 2 kWh for cleaning (as shown above). Total energy consumption after the retrofit was 3.3 kWh per day. During summer use, the upgrade makes a difference of 12.7 kWh per day (i.e. 16 – 3.3 = 12.7) in pump energy savings.
