PURPOSE: To display electric power consumption of each product, by obtaining a transition table corresponding a detected amount of operation of each product to a power consumption per unit time and obtaining the power consumption through the use of this table.

CONSTITUTION: For example, as a component using a steady power consumption for a cooler, a control circuit is said component, and the components for non- steady power consumption are compressor, indoor fan and outdoor fan. The power consumption of each component in the unit time is taken as P0WP3. The P0 is a constant, which is experimentally determined. As to the P1WP3, the numbers of revolution are taken as the detection amount as V1WV3 and the relation of correspondence are determined with the P1WP3 from experiments and the data are set to a computer system as tables T1WT3. A computer 40 samples V1WV3 at each unit time, P1WP3 are calculated referring to T1WT3 and the integrated power consumption P is obtained and displayed on a display 70. Thus, the power consumption of each product can be displayed.