Are Bigger Pool Pumps Better?

If you are in the process of installing a new pool or replacing your existing pump or motor, you may be wondering what size pool pump to purchase. While the tendency is “to be on the safe side,” and oversize, bigger pool pumps are worse for your pool AND for your wallet.  

Why is it important to choose the right sized pool pump?

A pool pump that is larger than needed has a more powerful motor and circulates water at a higher flow rate. This uses significantly more energy to pump the same amount of water and puts additional stress on your pipes and filter, meaning you’ll need to replace them sooner. When the flow rate is too high, your filter works less effectively and your pool’s clarity will suffer, which is a potential sign that your pool pump may be oversized. If an installer tries to sell you a larger pool pump as an “upgrade,” make sure to ask if it is necessary for your pool’s operation. 

Similarly, the rated horsepower of your current pump is not a good indicator of what to look for in a replacement. The original installer may have oversized the previous pump, and newer ones tend to pump water more efficiently, meaning a pump with a smaller motor may deliver the same flow. Furthermore, before 2021 motor horsepower ratings were not standardized, so manufacturers sometimes rated a pump with the same motor at two different horsepowers. Therefore, a lower horsepower pump may be comparable with your current pump, so don’t be surprised if your installer recommends one with what seems to be a smaller motor. Remember, lower horsepower pumps will generally use less energy and are the better option if they can meet your pool’s filtration and cleaning needs. When comparing two pool pumps, the best way to determine relative efficiency is to compare the Weighted Energy Factor (WEF), which is a metric like ‘miles-per-gallon’ for cars. A higher WEF indicates a more efficient pump.  

What about variable speed pumps?  

Variable speed pool pumps (including most ENERGY STAR certified models) can operate at a wide variety of speed settings, which makes sizing less complicated. Your installer will set the pump to operate at a speed that is right for your pool. Because they can be set to operate at lower flow rates most of the time, variable speed pumps will use much less energy than single speed and will also be better for your pool and your filter. 

To sum it up, you will generally want to consult with a professional contractor when selecting and installing your pool pump, but if you ever have a choice, go with the smaller pump and choose a model that has earned the ENERGY STAR – your pool and your wallet will thank you!  

For more guidance on finding the right pool services contractor, consult the ENERGY STAR Pool Pumps Fact Sheet (PDF, 2.1 MB) and our Buying Guidance

Author: James Kwon, ENERGY STAR Certified Products