Even with properly functioning timers, older single-speed pumps use a lot more energy than newer two-speed or variable-speed pumps. The only way to control a single-speed pump is to turn it on or off. As you would expect, variable-speed pumps can operate at several speeds, from full on to slow and easy. Slower speeds use a lot less energy but there are still times during the daily cycle when more pumping power is needed. Matching the demands of the pool with the speed of the pump is more efficient and saves money.

Saving money is a very good reason for using a variable-speed pump and it can be easily installed on an existing pool. Costs vary, but as with many energy-efficiency upgrades, it does not take long to recoup the investment. There also are instant rebate incentives from NV Energy, up to $200 for installing an efficient variable-speed pump. According to its Web site, www.nvenergy.com, there are several benefits to the homeowner. First of all, savings of as much as 80 percent on energy costs can be realized. Variable-speed pumps run cooler and quieter, extending their life. Filters can work more efficiently, keeping pool water more clean, clear and healthy.

As a former pool owner, I can attest to the noise of some single-speed pumps since the one I had drove me crazy at times. As they say, silence is golden, and I would have been very grateful for a quieter pool pump. These new pumps are very quiet. Some variable-speed pumps even include a safety feature to help prevent pool entrapment. Capable of sensing blockage of the drain, the pump's control system automatically shuts it down. This feature alone can justify the cost for safety-conscious pool owners.

Variable-speed pumps can come with a variety of options including programmable micro-processor control with password protection. Some pumps offer automatic sensing and protection from freezing, overheating, loss of prime and even voltage irregularities. They can be reprogrammed to adapt to changes in pool equipment. For pools with water features, programmable pumps can offer different modes of operation to easily change the sights and sounds of your pool.

Some manufacturers have savings calculators on their Web sites. I compared two of them, using the following assumptions for an existing pool: a 20,000 gallon pool with a single-speed, 2 horsepower pump running 10 hours per day all year with an electricity rate of 12 cents per kilowatt-hour. The Hayward calculator estimated yearly savings of $643.41 and a payback of 20 months (and only four months for the less costly two-speed option). The Pentair calculator estimated a range of yearly savings from $259.57 to $888.70 depending on chosen water turnover rates.

While actual savings will vary, there is no doubt that using an efficient pool pump makes good financial and environmental sense, especially when coupled with the rebates from NV Energy. There are other options as well. A simple pool cover can reduce evaporative losses and chemical use while keeping temperatures comfortable. Solar pool heating systems can save thousands of dollars and tons of CO₂.

As we enter pool season, think about what you can do to keep your pool clear, blue, clean and most of all -- green! It should no longer be a riddle.

Steve Rypka is a green living consultant and president of GreenDream Enterprises, a company committed to helping people live lighter on the planet. Steve can be reached via e-mail at steve@greendream.biz. More information relating to this column is posted at www.greendream.biz.