Storage apparatus and estimating method of power consumption for storage apparatus

Power consumption is calculated in accordance with an operation state of disk devices without using a power meter in a storage system. The power consumption in accordance with the operation state is calculated as follows. That is, information on the power consumption for every type of hard disks is stored in advance when types of I/O process (random/sequential of read and write) operate at idle time up to a limit state in every type of hard disks. A control unit of the storage system aggregates time waiting a response from the hard disks in every type of I/O process. The power consumption of the disks is calculated on the basis of the information on the power consumption stored in advance and a sum of the waiting time of the response from the hard disks.