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Solar pool heater has 3- to 5-year payback

April 27, 2003 - Clark County Public Utilities

Dear Energy Adviser: I attended your recent evening presentation on solar options in Clark County. You didn't touch much on solar pool heaters. I heat my swimming pool with an electric heater. Would converting to a solar pool heater decrease my pool heating costs? How expensive is a solar pool heater?

Answer: Swimming pools are a lot of fun, providing you and your family with exercise, entertainment and possibly even some therapeutic benefits. Unfortunately, in Clark County the outdoor swimming season is pretty short unless you heat your pool. As you have discovered, that can get expensive, even if you're only doing it during the normal summer season, June through August.

Using a solar water heating system is very cost-effective. In the case of your electric heater, payback on a solar pool heating system should be between three and five years at today's electricity rates, depending on the temperature and how long you heat your pool. Since the sun's heat is free, after the initial investment in the solar system it really costs nothing to heat your pool.

Solar pool heating systems are very simple. Instead of diverting pool water through a standard heater, the pool's existing filtration system pumps water through solar collectors, and the collected heat is transferred to the pool. Because solar pool-heating collectors operate just slightly warmer than the surrounding air temperature, these systems typically use inexpensive, high-flow, low-temperature collectors made from specially formulated plastics.

The only moving part of the system is a diverting valve. This valve determines whether water circulates through the collector loop. When the collector temperature is sufficiently higher than the pool temperature - generally about six degrees - water is pumped through the collector loop. When the sun goes down or cloudy weather keeps the temperature in the collectors low, the water bypasses them.

The diverting valves can be controlled manually, with timers, or more commonly by electronic sensors and controls.

To heat your pool most efficiency, the solar collectors should face south. If you have only western exposure, you can gain enough solar energy during the summer to heat your pool, but the system will require 10-20 percent more collector area.

"I size my systems between 60 and 75 percent of the pool's surface area to get maximum performance," says Andrew Koyaanisqatsi of SOLAR ENERGY SOLUTIONS, INC. (503-238-4502) in Portland. "Some companies will size at 40 percent of the pool size, which is cheaper initially, but doesn't keep the pool as warm or heat it for as long as a larger system. My customers are pretty happy with their systems. Once they've used a solar pool heater, they never go back to their old heater." Koyaanisqatsi recommends that pool owners use floating blankets on their pools at night to retain heat.

A solar pool heating system for an average pool (16 by 20 feet or 20 by 40 feet) will cost $3,000 to $5,000 installed.

Clark Public Utilities offers a loan program for customers who want to convert from electric to solar heating.

"For customers with an electric pool heater, converting to a solar pool heater is one of the most cost-effective things they can do to reduce their electricity bill during the summer," says Bob West, an energy counselor with Clark Public Utilities. "Not only do you reduce your electricity bill, but you lower your maintenance costs as well. Solar pool heaters are one of the best kept secrets in Clark County."