A method for monitoring power used by a power monitoring system is provided. The method includes receiving preset information that defines periods in which one or more preset electric devices are scheduled to operate, and obtaining a power use rate indicating how much power is used in each period. Further, the method includes generating an alternative instruction to decrease estimated power consumption in a target period in which the power use rate increases. The estimated power consumption is estimated power consumption in the building in the target period in which the power use rate increases, using power consumption information, to which power consumption of the electric devices to be preset is registered in advance, and the preset information. The alternative instruction is displayed on a display of a terminal apparatus.