Home energy savings and low CO2 emissions are indispensable against global warming. This paper proposes a home energy conservation support system by using ubiquitous sensors. This system encourages energy conservation to the residents by indicating the non-energy conservation activities and the estimated loss money. This system is composed by human activities & environment monitoring system and energy-saving advice system. Human activities & environment monitoring system detects non-energy saving activities by using ubiquitous sensors. The energy-saving advice system instructs the user energy-saving activities, which he should do by taking account on his non-energy saving activities. We confirmed the efficiency of the proposed system by experiments.