A measured value for a PMV within a living space is sent to a comfort efficacy evaluating device. Occupancy information (the current number of occupants N) in the living space is sent to the comfort efficacy evaluating device. The comfort efficacy evaluating device calculates a comfort index P as P=1.0−|PMV| / 3, and this comfort index P is weighted by the number of occupants N at the time that the comfort index P was taken. In this case, if the number of occupants is relatively high, the weighting is high, and if the number of occupants is relatively low, then the weighting is low. Additionally, the weighted comfort index P is integrated over an evaluation interval, and thus integrated value, or a weighted average based on this integrated value, is used as a comfort efficacy index TP. An evaluation of the efficacy of energy conservation can be performed in the same way, taking into account the current occupancy of the living space.