Power supply system and method for collective building

A power supply method for a collective building that is a method of supplying power to common loads for common purposes of a large number of households constituting a collective building and to separate loads for separate purposes of the households, the power supply method comprising:

• a power production step in which power is produced at at least one of first and second new renewable energy facilities;
• a power storage step in which the first and second new renewable energy facilities is stored in an energy storage system;
• a power assignment step in which the power stored in the energy storage system excluding power supplied to the common loads is equally assigned to the households;
• and
• a power supply step in which the power assigned to the households is supplied to at least one of the common loads and the separate loads of the households,
• wherein, in the power production step, the first new renewable energy facility that does not require an operation cost for producing power is always operated and the second new renewable energy facility that requires an operation cost for producing power is selectively operated.