The ability to heat pool water with solar energy is expanding.

While the use of solar panels has become fairly common, some pool owners are now using the sun to power their pool pumps. And recently, a Hawaiian condo complex has the first commercial pool in the United States to run solely with solar power.

Hawaiian Shores Community Association vice president Dave Johnson said the group made the decision to switch to solar power when they took a look at their electric bill, which was in the neighborhood of $1,400 a month. In addition, the complex, in the town of Pahoa, has frequent power outages because of weather and infrastructure problems.

With the new system, the association’s electric bill is about $145 a month. “The electric company didn’t send a bill the first month because they thought they’d made a mistake on the reading,” Johnson said.

Hawaiian Shores, on the big island of Hawaii, opened its pool Sept. 22. The pool’s three pumps are powered by 48 3-by-5-foot solar panels. There’s no heater, and since the pool’s open only during the day, no lighting, so the pumps are the only part of the pool that requires electricity. The association expects to recoup the money it spent on the system in power savings in about eight years, Johnson said.

Because the pool’s power comes exclusively from the sun, the pumps can run only when the sun is shining.

To run directly on solar power without inverters or batteries, the pumps had to be able to operate on minimal power and on direct current (DC). The installation has three Lorentz PS1800 pumps, each connected to 16 solar panels. An average residential setup requires about 45 square feet of solar panels to run a pump turning over the water once a day, according to Eric Macias, (title) with American West Windmill and Solar, the pump’s distributor. (right?)

But the more common way to save money with solar power still lies in its ability to heat pool water, and consumer demand for those systems remains relatively steady, according to market data and solar installers. In 2010, nearly 30,000 solar pool heating systems, both on new and existing pools, were installed in the United States, according to a study commissioned by the Solar Energy Industries Assn.

“People see it, they understand it, and they see what it can do,” said Ethan Horwitz, president of Solar Living, a solar firm based in Netcong, N.J., which installs approximately 100 solar pool heating systems annually. “It comes down to wanting to save money.”

“Our customers really fall into two different camps: those who have heaters and are sick of paying outrageous summer or fall [pool heating] bills and people who have never had heaters,” Horwitz said.

Installing solar pool heating typically costs between $4,000 and $6,000, according to Horwitz, with an expected payback time of one to two years, when compared to traditional pool heating systems. “You’re saving $1,500 a year in gas bills, and the whole system will last 20 years,” said Frank McLaughlin, owner of All Quality Solar Systems in Stone Harbor, N.J. “Even when the economy was really, really down, our business was great because of the economics of this.”

In 2010, the market for U.S. solar pool heating added up to $156 million, according to a 2011 report by the Solar Energy Industries Association in Washington, D.C.