To prevent the increase of a space caused by installing a plurality of watthour meters to the power supply by a plurality of power generation companies, and to improve the use convenience.

The purchase plan information 3 which is a planned information in purchasing the power is stored in a storage unit 12, and the power consumption is specified for every power generation company based on the purchase plan information 3 by a control unit 15. The information on the power consumption is displayed on a display panel 16. In addition, a setting instrument 2 having a set input unit 21 for setting and inputting the purchase plan information 3, a transmission unit 23, etc., is prepared, and the purchase plan information 3 transmitted from the setting instrument 2 is received by a reception unit 11 of the watthour meter 1 and stored in the storage unit 12.