Tokyo Electric Power Co. and nine other utilities emitted 5.3 percent less carbon dioxide as power demand slumps amid the global recession.

The generators emitted 395 million metric tons of carbon dioxide in the year that ended in March, compared with 416.9 million tons a year earlier, according to Bloomberg calculations using data released by the utilities. In the previous year, power generation accounted for 30 percent of Japan's overall greenhouse-gas emissions.

The nation's electricity output fell 3.2 percent in the year that ended March 31, including a 6 percent drop in production at thermal generators, according to the Federation of Electric Power Companies. Prime Minister Taro Aso has pledged to cut carbon emissions by 15 percent from 2005 levels, or the equivalent of 8 percent from 1990 levels, by 2020.

"We want companies to take additional measures to achieve Japan's 2020 emission-reduction goal," said Yuta Okazaki, deputy director of the climate policy division at the Environment Ministry. "This decline doesn't result from climate-change protection measures, but only from the economic downturn."