Japan’s obsession with conservation stems from an acute sense of insecurity in a resource-poor nation that imports most its energy from the volatile Middle East, a fact driven home here by the 1970s shocks. The guiding hand of government has also played a role, forcing households and companies to conserve by raising the cost of gasoline and electricity far above global levels. Taxes and price controls make a gallon of gasoline in Japan currently cost about $5.20, twice America’s more market-based prices.

The government in turn has used these tax revenues to help Japan seize the lead in renewable energies like solar power, and more recently home fuel cells. One way has been a subsidy of about $51,000 for each home fuel cell. This allowed Mr. Kimura to buy his cell last year for about $9,000, far below production cost. His cell, which generates one kilowatt-hour of energy per hour, provides just under half of his household’s electricity, and has cut his electricity bill by the same amount, he said.

The device works by converting natural gas into hydrogen, which the fuel cell then uses to generate electricity. Heat released by the process is used to warm water.

The first two fuel cells were installed in the prime minister’s residence in April 2005. Since then, some 1,300 have been sold, according to the trade ministry. The ministry forecasts that as sales pick up, production cost will fall to about $5,000 by decade’s end. Experts say that Japan is far more willing to embrace new technologies than the United States, where opposition to hydrogen storage tanks in Tarrytown, N.Y., forced General Motors to scrap an experimental filling station for fuel-cell cars last year.

Image Kiminobu Kimura of Tokyo uses a home fuel cell, a machine that resembles a filing cabinet and sits in front of his house. Credit... Ko Sasaki for The New York Times

Higher energy prices have also created strong domestic demand in Japan for more conventional and new energy-saving products of all sorts. That has spurred the invention and development of things like low-energy washing machines and televisions and high-mileage cars and hybrid vehicles, experts say. Japanese factories also learned how to cut energy use and become among the most efficient in the world.

Companies like Mitsubishi Heavy Industries are now reaping the benefits in booming overseas sales of their highly efficient electric turbines, steel blast furnaces and other industrial machinery, particularly in the United States. The environment ministry forecasts that exports will help turn energy conservation into a $7.9 billion industry in Japan by 2020, about 10 times its size in 2000.