As leaders of the world’s most powerful nations discussed climate change at the Group of Eight summit in northern Japan last week, Japan’s big tech companies displayed some of their most cutting-edge solutions in a nearby “zero-emissions house.”

The single-story, 2,152-square-foot house generates all the energy required for a family of four, therefore eliminating carbon-dioxide emissions, according to the Japanese government.

Products inside, many already on sale in Japan, include a washer that requires no water and an air conditioner that senses where people are in a room and automatically sends cool air in their direction rather than cooling empty space. Yet the eco-friendly products also carry a steeper price tag than traditional appliances.

The house uses a wind-turbine generator and a photovoltaic generation system, which directly converts light into electricity, to produce about 15 kilowatts of energy a day, nearly five times the amount used by a regular household. The government has presented the house as one of its contributions toward helping the world cut greenhouse emissions in half by 2050.

The zero-emissions house is an attempt by Japan’s big tech companies to showcase their recent and growing focus on environmental technologies as a future area of growth.

The waterless washer is Sanyo Electric Co.’s latest Aqua washer/dryer, a three-in-one machine that uses high-powered air, or ozone, to wash clothes without a single drop of water. The process of “ozonation” — which disinfects bacteria on contact — can air-wash clothes, removing about 80 percent of biodegradable stains without using any water at all, says Ryo Hagiwara, Sanyo’s spokesman.

The company says a full-cycle of air-wash uses about twice as much electricity as a regular wash, but only one-fifth the total energy of a comparable full wash and dry — in part because the air wash doesn’t need a drying system.

The Aqua washer also has a regular wash setting that can purify and recycle water that had been used for a bath, thus reducing the amount of fresh water required by the machine to a mere half-bucket.

The machine is available only in Japan and Taiwan, but the company says it hopes to make inroads eventually in the U.S. and Europe. Sanyo’s Aqua washer costs 228,000 yen ($2,135) or about 80 percent more than an equivalent washer/dryer on the Japanese market.

The air conditioner is the new, human-sensing air-conditioner by Mitsubishi Electric Corp., which detects a person’s motion and location using heat sensors. The machine, which is available only in Japan, then emits air waves specifically targeting the people. That can save up to 50 percent in energy use, the company says. Still, the air conditioner, which is built into a wall, costs a lofty 200,000 yen ($1,873), or about a third more than conventional air conditioners.

There’s also a low-energy television set. Sharp Corp., a leading solar-panel producer, is showing one of the world’s thinnest liquid-crystal-display TVs, with a thickness of about three-fourths of an inch. The set, not yet on sale, consumes only half the energy of existing models, the company says.

Sharp is also showing a solar-energy array whose solar cells can be made semitransparent, so they can be put into a window.

Some ideas are simple. Sekisui House Ltd. is displaying a roof-top vegetation system that uses a thin film of moss grown on tile plates attached to the roof of the house.

The housing company says the moss, which can be fitted alongside solar panels on the rooftop, can lower the temperature inside the house by one degree Celsius, helping reduce air-conditioning use. The company plans to start sales in Japan soon.