While Japanese utilities’ lost generation capacity due to nuclear-reactor shutdowns has not affected Tokyo-area data centers, it may become an issue in the summer, during peak demand.

In a letter Japan Data Center Council sent to the nation’s Ministry of Economy, Trade and Industry (METI) several days after the 9.0-magnitude earthquake and tsunami on 11 March, council officials said ensuring adequate fuel supply to keep data centers running could become problematic if rolling blackouts were to be implemented.

JDCC is a consortium of data center builders and operators in Japan. It has more than 120 members, including Softbank, Equinix Japan, NEC, Fujitsu, Hitachi and Yahoo!. Power utilities Kansai Electric Power and Tokyo Electric Power (TEPCO) are also members.

According to AltaTerra analyst Zen Kishimoto’s translation of parts of the letter, there are about 50 data centers in the Tokyo metropolitan area. If each facility that required 10,000VA started a generator, about 5,000-6,250 gallons of fuel would be consumed per hour total, JDCC wrote.

With each blackout lasting about three hours, eight such interruptions would exhaust many facilities’ on-site fuel reserves. Some data centers store enough fuel to run for 48 hours and some have enough only for 24 hours.

"After eight power interruptions, securing enough fuel would become extremely difficult," Kishimoto’s translation reads. "To transport this much fuel, a few large trucks are needed. If the demand happens at the same time for all the data centers, it would be a logistical nightmare."

JDCC sent the letter on 18 March, asking to be exempt from blackouts utilities have been implementing since the disaster struck to avoid a total power outage.

No blackouts have so far been implemented in areas of Tokyo with high concentration of data centers, but come summer, generation capacity shortages may cause the issue to resurface, Kishimoto told DatacenterDynamics.

TEPCO, supplier of about a third of all electricity in Tokyo and the surrounding area, is expected to be able to provide about 10m kW less power than the expected demand of 60m kW during peak hours in July and August, according to a report by the Financial Times.

An anonymous Japanese government official told Reuters that METI was mulling a plan to require large industrial electricity users to cut their power use during summer peak hours by 25% to avoid potential blackouts during the season.