TOKYO - Facing a summer power crunch, some Tokyo city government employees began working an hour earlier Monday to conserve energy amid shortages caused by damage to a tsunami-hit nuclear plant.

City workers on the earliest shift will start at 7:30 a.m. and be allowed to leave at 4:15 p.m.

By better exploiting the early daylight hours this summer, city officials hope to use less air-conditioning and less office lighting at night.

"It should be a good thing, and it doesn't require any cost," Tokyo's outspoken Gov. Shintaro Ishihara said Friday. "I think all of Japan should shift to summertime hours."

To prevent blackouts after the March 11 earthquake and resulting tsunami, which knocked out Tokyo Electric Power Co.'s Fukushima Dai-ichi nuclear plant, the central government asked companies and government offices to cut electricity usage by 15 percent. It wants companies to limit air-conditioning and set room temperatures at 82 degrees.

Officials are also encouraged to follow a new dress code called "Super Cool Biz" launched last week that includes lighter clothing, such as polo shirts, Hawaiian shirts, and even sneakers instead of the traditional tie and jacket.

Households across Tokyo are urged to use electric fans instead of air conditioners, unplug appliances when not in use, and raise temperature settings on refrigerators.

TEPCO expects to supply 53.8 million kilowatts for Tokyo and its vicinity in July, which is short of an estimated demand of 60 million kilowatts. Tokyo uses one-third of TEPCO's output.

Ishihara has set a more aggressive target of a 25 percent reduction in energy use for Tokyo, and officials hope the new hours for government workers will spill over to the private sector.

"To set a good example, we shouldn't keep lights on at our offices until late," city official Hideo Ishii said.

About 9,500 employees at the city's headquarters will be fully participating by the end of the week. By July, that will grow to 25,000. It will exclude teachers, police, firefighters, and medical experts.

While employees will start work earlier, the clocks inside city hall won't change.

Still, Ishihara would like to take the experiment a step further and establish daylight saving time, shifting clocks forward during summer as many Western nations do.

Changing the clocks in the summer is debated in Japan, with most sentiment opposed.

Daylight saving time was imposed in 1948 under the U.S. occupation after Japan's defeat in World War II but lasted only four years because it was so unpopular. It has since been remembered negatively.

More important, under Japan's corporate culture, many workers feel obligated to work until it is dark outside - no matter what their starting time.

But that may change this summer at Tokyo's city hall. A team of officials will be dispatched to offices with lights on after 6:30 p.m. to urge employees to leave.