“Japan taught itself decade s ago how to compete with gasoline at $4 per gallon,” said Hisakazu Tsujimoto of the Energy Conservation Center, a government research institute that promotes energy efficiency. “It will fare better than other countries in the new era of high energy costs.”

According to the International Energy Agency, based in Paris, Japan consumed half as much energy per dollar worth of economic activity as the European Union or the United States, and one-eighth as much as China and India in 2005. While the country is known for green products like hybrid cars, most of its efficiency gains have been in less eye-catching areas, for example, in manufacturing.

Corporate Japan has managed to keep its overall annual energy consumption unchanged at the equivalent of a little more than a billion barrels of oil since the early 1970s, according to Economy Ministry data. It was able to maintain that level even as the economy doubled in size during the country’s boom years of the 1970s and ’80s.

Japan’s strides in efficiency are clearest in heavy industries like steel, which are the nation’s biggest consumers of power. From 1972 to 2006, the Japanese steel industry invested about $45 billion in developing energy-saving technologies, according to the Japan Iron and Steel Federation.

The results are visible at the Keihin mill on Tokyo Bay, run by Japan’s No. 2 steelmaker, JFE Steel. Massive steel ducts snake from the blast furnaces and surrounding buildings. These capture heat and gases that had previously been released into the air or burned off as waste. Now, they are used to power generators that produce 90 percent of the plant’s electricity. (The plant’s main fuel remains the coal used to heat its huge blast furnaces.)

Such innovations allow the mill to produce a ton of steel using 35 percent less energy than it did three decades ago, said Yoshitsugu Iino, group leader of JFE Steel’s climate change policy group. Mr. Iino calculates that if the global steel industry adopted Japanese conservation measures, it could reduce carbon emissions by some 300 million tons a year.

But even with corporate efficiency gains, Japan’s emissions of carbon dioxide, the main greenhouse-gas emission from human activities, have grown, largely because of rising living standards and continued reliance on coal, according to climate scientists. James E. Hansen, NASA’s leading climatologist, sent an open letter to Mr. Fukuda on Thursday seeking a greater commitment to emissions cuts.