NOVELTY - The data center (20) has a device driven by electric power. A storage battery stores the electric power. A controller switches operating mode of the device over course of time based on predicted values for the amount of electric power generated using renewable energy, the amount of electric power stored in the storage battery, and the amount of electric power consumed by the device. The controller determines a predicted value for the amount of electric power stored in the storage battery at time based on amount of electric power generated by the renewable energy.    USE - Data center for being operable by electric power based on renewable energy e.g. solar power and/or wind power.    ADVANTAGE - The data center ensures stable execution of jobs to be processed while predicting the amount of electric power to be supplied to data centers by using electric power based on renewable energy, where the operating mode of the device is switched over based on predicted values for the amount of electric power generated using renewable energy, the amount of electric power stored in the storage battery, and the amount of electric power consumed by the device, where operation of the device remains stable relative to changes in the amount of electric power being supplied, so that operation of the device can be maintained at a minimum level for an increase in the amount of generated power stored in the storage battery when the amount of electric power stored in the storage battery is low, thus supplying the power stably and continuously to the data center based on a prediction of the amount of electric power stored in the storage battery even when the amount of electric power generated changes due to weather conditions.    DETAILED DESCRIPTION - INDEPENDENT CLAIMS are also included for the following:    (1) a method for distributing a load between data centers    (2) a computer program product stored with a set of instructions to perform a method for distributing a load between data centers.    DESCRIPTION OF DRAWING(S) - The drawing shows a schematic view of a data center network system.    Communication network (10)    Data centers (20, 22, 24, 26)    Computers (30, 32)    Network system (100)