TOKYO -- Virtually self-sufficient "zero-energy" homes are drawing attention in Japan as the country stares harder at a strict emissions reduction target in the Paris Agreement, a U.N. climate accord reached late last year. The Japanese government is hoping these energy-efficient homes catch fire, so to speak, by 2020.
A zero-energy house in a residential district of Yokohama, south of Tokyo, looks like a lot of other houses, except it has a solar power system on the roof. Inside, Hisao Yamashita looks at how much electricity his roof is collecting by checking a terminal connected to a home energy management system, or HEMS.
The terminal keeps Yamashita informed. It tells him, for instance, that his house has essentially kept 255 liters of kerosene from being burned to generate electricity.
The house is equipped with a fuel cell, which can efficiently produce power and supply hot water. Sunlight comes in through double-glazed window panes that are highly heat-insulating. All the lamps in the house are energy-saving light-emitting diode fixtures. The walls are packed with high-performance insulation. And an efficient air conditioning system keeps room temperatures at comfortable levels.
But since the entire structure is highly insulative, "I rarely turn on the air conditioner during the summer or [heat the place during] winter," Yamashita said. "Still, it's comfortable."
It is also something of a revenue stream. Last year, Yamashita generated a net surplus of 70,000 yen ($685), thanks to the system.
Japan's Ministry of Economy, Trade and Industry has set criteria that a house must meet before it can be dubbed zero-energy. It has to:
- Be at least 20% more energy efficient than an ordinary home.
- Be airtight and adiabatic enough to increase the efficiency of air conditioners and water heaters.
- Allow for efficient ventilation.
- Have a solar power or other renewable energy system that can keep the house from sipping electricity from the grid, or even spit some electricity back onto the grid.
Late last year, the economy ministry wrote a road map to help Japanese build more zero-energy homes, and last month the government responded to the Paris Agreement by laying out a plan to slow global warming. In it, the government said it will "aim to make more than half of new built-to-order homes zero-energy homes by 2020." The ministry wants about 50,000 zero-energy homes to be going up on an annual basis by 2020.
Since the oil shock of 1973, energy consumption in Japan has fallen by 20% in business districts but doubled in residential areas. Although electric appliances have become increasingly energy-efficient, the number of devices per household has grown, as have the number of households.
To encourage people to build zero-energy homes, the government has been doling out 1.25 million-yen subsidies to each household wishing to build one in the current fiscal year. Two years ago, when Yamashita built his home, he received subsidies from the central and prefectural governments. He managed to save 2 million yen.
Kenichi Ishida, a managing officer at Sekisui House, the builder that put up Yamashita's home, said zero-energy homes "can reduce energy use to zero without compromising on comfort." The company reckons its zero-energy homes can reduce power usage by 40% to 50% compared to most homes today and that the sun can supply all the energy they will need. Of all the new custom-built homes the company constructed in fiscal 2015, over 70% were zero-energy.
It appears these homes will grow in popularity. But the current boom owes much to the government subsidies. For more of the homes to be built, costs must come down, especially those associated with all the energy-saving equipment and materials.
Once prices do come down, once it becomes easier for home buyers to recoup their initial outlays, once energy management systems open people's eyes to how much lower utility bills can be, more people will take the zero option.