TOKYO — Facing a power crunch and a scorching summer, some of nearly 10,000 Tokyo city government employees started their work shifts an hour earlier today to conserve energy amid shortages spawned by the damage to a tsunami-hit nuclear plant.

Government workers’ on the early shift start at 7:30 a.m. and will 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 office lighting at night.

“It should be a good thing, and it doesn’t require any cost,” Tokyo’s outspoken Gov. Shintaro Ishihara said. “I think all of Japan should shift to the summer time hours.”

To prevent blackouts in the wake of the March 11 disaster, which knocked out Tokyo Electric Power’s Fukushima Daiichi nuclear power plant, Japan’s central government has asked companies and offices to cut electricity usage by 15 percent. It wants companies to limit air conditioning and set room temperatures at a warm 82 degrees Fahrenheit.

Officials are also encouraged to follow a new dress code called “Super Cool Biz” launched last week that urged employees to wear lighter clothing, such as polo shirts, Aloha shirts and sneakers instead of the traditional tie and jacket.