Tohoku Electric Power Co., Inc. is an electric utility, servicing 7.6 million individual and corporate customers in six prefectures in Tōhoku region plus Niigata Prefecture. It provides electricity at 100 V, 50 Hz, though some areas use 60 Hz. Tohoku Electric Power is the fourth-largest electric utility in Japan in terms of revenue, behind TEPCO, KEPCO and Chubu Electric Power. Wikipedia