Wholesale electricity markets area in Japan firmed up in the week ended May 22, bolstered by reduced supply from photovoltaic (PV) power plants under overcast skies. 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 6.10 yen per kilowatt hour (kWh), up 0.19 yen/kWh or 3.2 % from the previous week, meanwhile prices in the western, made up of the Chubu, Hokuriku, Kansai, Chugoku, Shikoku and Kyushu area, at 4.24 yen/kWh, up 1.13 yen/kWh, or 36.3%. Markets had fewer units (one unit = 30 minutes) of 0.01 yen/kWh, the lowest price under current regulations, on the Japan Electricity Power Exchange (JEPX). Tokyo area's prices, however, bucked this week's trend, due to low temperatures and technical factors.

The minus premium of Hokkaido to Tokyo narrowed to 0.29 yen/kWh from 1.28 yen/kWh observed in the week ended May 15. with Hokkaido's average 5.85 yen/kWh (previous week's ave:5.00 yen) and Tokyo's 6.14 yen/kWh (6.28 yen), which are reckoned in conformity to data compiled by the JEPX. Hokkaido prices often move at higher levels than other areas especially in the winter season. Tohoku's average climbed by 1.02 yen/kWh back to 6.04 yen/kWh. Repair and checkback operations at connection lines between Tokyo and Tohoku, but the total ampacity seemed to increased compared to the previous week. This appeared to allow Tohoku area to send more electricity to Tokyo area. Additionally, Tokyo's daily maximum temperatures were forecasted on a day ahead basis at 17 degrees Celsius to 24 deg C compared to the previous week's range of 26 to 29 deg C. These circumstances dented Tokyo area's prices.

Kansai's weekly average moved up by 1.18 yen/kWh to 4.30 yen/kWh, and Kyushu's advanced by 0.92 yen/kWh to 3.93 yen/kWh. The gap of the two areas grew a touch to 0.37 yen/kWh from the previous week's 0.11 yen/kWh. Kansai area is the biggest market in the western Japan, and Kyushu's prices are apt to move at less expensive levels alongside of other areas. In both areas, daytime price gains were bigger than evening time's.

On JEPX, the weekday average of System Price (Day ahead 24 hours), which were figured based on the data of 9 areas, bounced back by 0.77 yen/kWh or 19.8% to 4.65 from the previous week's 3.88 yen/kWh, with the average volume increasing by 29,719 megawatts hour (MWh) to 723,884 MWh from 694,165 MWh recorded in the previous week.

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