By Steve Easley and Jeff Farlow
Some of these savings are a result of motor efficiency; however, another significant factor is that power consumption drops at a nonlinear rate as pump (motor) speed and water flow is reduced. In fact, when motor speed and flow rate is reduced by half, the power demand is reduced to 1/8 of the original power, at least in a laboratory setting.
Actual results in the field vary but often are around 1/7. Also, with less flow, the pump needs to run longer to achieve the same turnover for filtration purposes. As a result, the energy consumed will not be 1/8 when using half the flow, but can easily be 1/4. This is because the pump needs to run twice as long while consuming 1/8 of the power (i.e., 1/8 x 2 = ¼).
In other words, by running the pump slower, even though it will be operating longer, the lower speed translates into dramatic savings in energy consumption and operating costs. Plus, variable-speed pumps have higher quality motors—not only are they remarkably quiet, they also last longer, putting less strain on the filter, plumbing and other parts of the system.
Read the full article: The case for pump upgrades