A technique for determining task allocation for reducing power consumption of an entire system is disclosed. This system includes physical computers, a cooling apparatus for cooling the physical computers, and a power-saving control server for controlling the physical computers and cooling apparatus. The power-saving control server includes a virtual server layout generator which sets up a plurality of sets of task allocations with respect to the physical computers, a server power calculator for calculating power consumption of the physical computers in each task allocation, a physical computer profile used to estimate a heat release amount of the physical computers in each task allocation, a cooling power calculator which computes power consumption of the cooling apparatus, and a virtual server relocator which determines a task allocation with a total of calculated values of the server/cooling power calculators being minimized to be the optimum task allocation for the physical computers.