Hawai'i residents in every county are using less electricity this year than last — the first statewide decline in per-household power consumption since 1997.

Industry and utility officials say they can't be sure it's a result of high energy costs, but that's one conclusion that makes sense to them.

"It's logical that people would find ways to use less to deal with (increased costs), but it's hard to measure that," said Dave Waller, Hawaiian Electric Co. vice president for customer solutions.

One indicator of consumer desire to cut power bills is that more people are buying solar water-heating systems than at any other time in the last 30 years, said Cully Judd, owner of the state's largest and oldest solar equipment firm, Inter-Island Solar Supply.

But utility officials say the decline could have other causes. One is that last year's hot and humid weather made for heavy air-conditioner use, and power consumption reached record highs statewide. This year's reduction of less than 1.5 percent in average monthly kilowatt-hours could simply be a drawback from an unusual year, and it is notable that household electricity use this year is still higher than in 2003.

But Waller said the reduction also may be attributed to the widespread availability of energy-efficient lighting and electronics, and an indication that savings from the use of these products are finally taking hold.

It also could be that people are simply opting for conservation in response to the urging of utilities, government and environmental groups.

Waller said it's likely a combination of these factors, and he believes the change is significant.

"We've had a substantial increase in energy use for several years, and beginning in 2005 we began to see a moderation in energy use. Starting in the first quarter, we saw this trend reverse," he said.

ENERGY-EFFICIENT HOME

For 'Ewa Beach resident Denise McCurdy, electricity costs are driving her family's consumer decisions. Three weeks ago, they moved into an energy-efficient home built by Gentry Homes after their frustration at $400-a-month power bills in new but not energy-efficient military housing.

"Energy efficiency, that was important. The house that I had previously, the bills were outrageous, ridiculous," she said.

McCurdy's new home, Gentry's Tuscany design, has a solar water heater. It has exterior walls with insulation and a roof with insulation and a radiant barrier to reflect the sun's heat. All exterior windows use dual-pane glass that reflects solar radiation. Every room has a fan, but there is also a high-efficiency air-conditioning system.

Gentry's Tuscany and Montecito designs made it the first O'ahu residential developer to receive the U.S. Environmental Protection Agency's Energy Star certification, given to designs that are at least 30 percent more energy-efficient than the 1993 Model Energy Code.

"We've sold over 125 of these houses since May. The buyers definitely recognize the added value that can save them money every month," said Rick Hobson, Gentry's vice president of sales and marketing. "Everybody's trying to figure out how to build a better home. It differentiates your product from the marketplace."

But it's not only Gentry. Every major O'ahu residential developer is rolling out homes that have significant energy-efficiency features, said Fred Moore, president of the Building Industry Association of Hawai'i. That includes Castle & Cooke Homes, Haseko Construction and Schuler Homes, he said.

And while the cost of those additions may increase the overall price of a home, the consumer gets paid back in lower electric bills. A solar water heater alone can cut a family's electricity use by 30 percent to 40 percent.

"As the cost of fuel goes up, the payback time is getting shorter and shorter," Moore said. "Energy-efficiency solutions are becoming more affordable."

SOLAR WATER HEATER

The most effective technical fix for high energy costs is still the solar water heater. An electric or even a gas-fired water heater can be the biggest energy drain in a Hawai'i home.

"Even if you're running air conditioning, the hot water is really a big spike in your energy bill," Moore said.

A solar heating system, properly designed and installed, can cut the water heating cost out of the budget entirely most of the time, leaving gas or electric power available as a backup for extended cloudy periods or times of unusually high demand.

Rebate programs, approved by the state Public Utilities Commission, help pay part of the cost of solar water systems. Programs differ island by island but, for example, HECO on O'ahu will pay $750 of the cost of a system installed by an approved contractor. A typical system costs $4,000 to $5,000. There also is a 35 percent state tax credit on the cost, after deduction of the rebate.

Still, there are far too many homes without them, experts say.

"It might not work too well at the base of the mountains in Kahalu'u, but statewide, there are more homes that could use it than couldn't," Moore said.

ESTIMATED AT 70,000

HECO officials estimate there are 70,000 homes in the Islands that are outfitted with solar water heaters. Utility rebates have been paid on 28,000 of them in the past decade.

But solar water heater supplier Judd said that number underestimates the actual installations.

He said he knows "there are a lot of people who aren't with the program" but still have the systems.

"It's a no-brainer to put it on the house. As electric rates go up, it is economically ridiculous not to put in a solar," Judd said.

He said consumers clearly are getting the message. "We've sold more stuff in the last six months than in any six-month period in the last 30 years," he said.

McCurdy said the benefits of designed-in energy efficiency are clear to her family. They turn off the air conditioning in the daytime; when they come home, the house is comfortable enough to prepare dinner without turning on the air conditioner.

They do turn it on at night for sleeping, "because I like it cold," she said.

Reach Jan TenBruggencate at jant@honoluluadvertiser.com.