Japan has urged businesses and households in parts of the country to cut electricity use by up to 15% to avoid possible blackouts.
The country is facing power shortages this summer because its 50 nuclear reactors have been taken offline.
Public confidence in nuclear safety was shaken by the meltdowns at the Fukushima power plant, triggered by last year's earthquake and tsunami.
The call for electricity reduction will take effect from July to September.
This time around the move to save power is not mandatory, unlike cuts imposed in the eastern parts of the country last summer after the nuclear crisis.
It is in the heavily industrialised area of western Japan, served by Kansai Electric Power, that customers have been asked to cut electricity usage by 15%.
Chief Cabinet Secretary Osamu Fujimura, after a government meeting discussing power shortages, said that there was a "need to widely instigate power-saving measures" due to the shutdown of nuclear facilities.
"The government will try hard to figure out how to implement the measures decided today so that the power savings will affect the economy and people's livelihood as little as possible," he said.
"But I would like to repeat here our appeal to the nation to save power this summer."
Japan's last nuclear reactor went offline for routine maintenance two weeks ago and none have been switched back on so far.
The government has been reluctant to order restarts of the nuclear plants against the public's wishes, even as the scarcer and more expensive electricity could have a severe effect on Japan's economy, reports the BBC's Roland Buerk.
Surveys show that almost all big businesses expect their earnings to be affected, with some preparing to move more manufacturing abroad.
Before the Fukushima meltdowns, nuclear energy powered up to 30% of the country's electricity.
Prime Minister Yoshihiko Noda said on Thursday that he would decide soon on the restarting of two idle nuclear reactors at Kansai Electric's Ohi nuclear plant.