Due to extreme impacts of earthquake and tsunami on the Japanese electrical energy grid, power companies in Japan are putting into place scheduled outages to reduce their energy load.
"Illuminating Japan" weblog gakuranman.com, Great Tohoku Earthquake.
The TEPCO web site is under extreme load, and is throwing error messages on the main page: "An error occurred while processing your request. Reference #97.1c1fac41.1300025768.58c0d00". Deeper links appear to be less affected. Here is from a TEPCO news release of 3/13; this is data that could be mapped.
[Blackout in TEPCO's Service Area] Total of about 0.26 million households are out of power. Tokyo: 0 Kanagawa Pref.: 0 Tochigi Pref.: 7,366 Chiba Pref.: 301 Saitama Pref: 0 Gunma Pref.: 0 Ibaraki Pref: 247,853 Yamanashi Pref: 0 Shizuoka Pref: 0 (east of Fuji River) [Supply and Demand Status within TEPCO's Service Area to Secure Stable Power Supply] Backup supply from Shinshinano Conversion Station: 600MW Backup supply from Sakuma Conversion Station: 300MW Backup supply from Higashi Shimizu Conversion Station: 100MW Backup supply from Kitahon Interconnection Facility: 600MW
Schedule for Japan's Rolling Blackout. This unattributed PDF is all in Japanese, which I don't read; it appears to be a scan of a facsimile, and has all external indications of being genuine. The map below is excerpted from that original, and is from the TEPCO power service area. There is more excellent coverage (in Japanese) on Gigazine: 2011/03/13 Rolling Blackouts.
An even better map, in full color, via http://matome.naver.jp/odai/2130001740747617201
Japanese power grid, via gakuranman.com. Note that a portion of the Japanese grid is on 50hz, and another portion is on 60hz.