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A Tokyo-based chemical firm is building energy-efficient homes that it claims will allow occupants to virtually do away with monthly electricity bills.

The housing division of Sekisui Chemical Co. has been selling homes equipped with its “zero-cost-electricity system” since January. And power companies, once opposed to this type of arrangement, have welcomed the move.

The system combines a solar power generator, efficient water heater and airtight housing structure that maintains a constant temperature inside the home.

Surplus electricity produced by the solar system during the daytime is sold automatically to electric power companies. At night, the system automatically buys back electricity from the firms — at a third of the daytime charge.

After averaging out the differences in consumption between night and day, summer and winter, users are expected to break even over the course of a year, effectively paying nothing for electricity consumption.

Sekisui said it costs about 2.5 million yen extra to build a home with the power-saving system installed.

“A house owner with children pays nearly 250,000 yen a year for electricity charges,” said Kenichi Akiyama, manager of the corporate communication department at Sekisui Chemical.

“If you introduced our system, you could speed up returning your housing loans.”

Households using the system will therefore take 10 years just to break even, he said.

Integral to the setup is the heat-pump system for water heating, developed jointly by Tokyo Electric Power Co. and Denso Corp., an auto parts manufacturer based in Aichi Prefecture. Heating water accounts for nearly one-third of the home’s total energy consumption.

“The new heat-pump system is three to four times more efficient than conventional ones in terms of energy consumption,” Akiyama said.

Sekisui Chemical will build 2,000 new homes featuring the system this year, he said. The firm builds prefabricated homes.

While the concept of combining solar power and an airtight housing structure is not new, the business environment surrounding it has recently changed, according to Akiyama.

In 1999, the cost of a solar power system stood at 880,000 yen per kilowatt. By 2002, it had fallen to 480,000 yen per kw. The maximum output of the system is 5.5 kw, costing 2.64 million yen, Akiyama said.

Electric power companies grudgingly backed the system after a series of accidents and coverups at nuclear power plants forced Tepco to suspend operations to conduct safety inspections. The shutdowns are expected to cause a power shortage this summer.

Tepco once produced about 40 percent of the electricity for the Tokyo metropolitan area at its nuclear power plants in Fukushima and Niigata prefectures.

Sekisui Chemical’s system helps reduce, albeit slightly, the burden on power firms to produce and supply electricity.

Akiyama said this is why these firms have welcomed the new system and agreed to purchase surplus electricity generated by such homes.

The government has also agreed to subsidize purchases of the heat-pump system, he said.

If popular, the system will become cheaper still, thanks to economies of scale, according to Akiyama. The ongoing development of solar-power systems and energy-efficient home appliances will also help lower the cost of the system.

“It is time to disseminate our system to houses throughout the nation,” he said.

“We will introduce it to all of our two-story houses in the nation.”

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