Wholesale electricity markets in Japan clawed up in the week to July 10 due to record rainfall that shed supply from photovoltaics (PV). Based on the Rim Power Index (Day ahead 24 hours), the weekday power prices in the eastern market, including Hokkaido, Tohoku and Tokyo area, averaged out at 5.53 yen per kilowatt hour (kWh), up 0.58 yen/kWh or 11.7 % from the previous week, meanwhile prices in the western, made up of the Chubu, Hokuriku, Kansai, Chugoku, Shikoku and Kyushu area, at 4.95 yen/kWh, up 0.40 yen/kWh or 8.8%.

Torrential rain lashed Japan, especially western regions, bringing thick watery clouds. This resulted in less output from PV stations. But, in west Japan, factories, shops and so on were shut down as the downpour caused mudslides and floods, severing roads and leaving many houses. Thus, less power usage weigh on west prices. On the other hands, in east Japan, electricity producers appeared to dial back not only PV but also non-PV stations.

The premium of Hokkaido to Tokyo recorded minus 0.12 yen/kWh compared with plus 0.36 yen/kWh observed in the previous week, with Hokkaido's 24 hours average 5.43 yen/kWh (previous week's ave:5.29 yen) and Tokyo's 5.55 yen/kWh (4.93 yen), which are reckoned in conformity to data compiled by the Japan Electric Power Exchange (JEPX). Hokkaido's biggest city Sapporo had better weather, and PV stations provided more electricity, leading small loses for peak-time average. Hokkaido prices often move at higher levels than other areas especially in the winter season. Tohoku's average advanced by 0.57 yen/kWh to 5.50 yen/kWh, 0.05 yen/kWh less than Tokyo. Three areas' average prices for nighttime gained slightly.

Kansai's weekly average climbed by 0.38 yen/kWh to 4.95 yen/kWh, and Kyushu's advanced by 0.51 yen/kWh to 4.95 yen/kWh. The differential of the two areas disappeared compared with 0.13 yen/kWh observed in the prior week. Kansai area is the biggest market in the western Japan, and Kyushu's prices are apt to hover at less expensive levels alongside of other areas. Both areas' average for nighttime were edged down.

On JEPX, the weekday average of System Price (Day ahead 24 hours), which were figured based on the data of 9 areas, moved up by 0.54 yen/kWh or 11.6% to 5.20 from the previous week's 4.66 yen/kWh, with the average volume decreasing by 20,046 megawatts per hour (MWh) to 911,879 MWh compared to the previous week.

Rim Power Report (English Language Version) click

＊RIM Power Report: Sample (English Language Version - Available!) click