The purpose of this study is to investigate extrinsic and intrinsic motivation factors relating to long-term household energy-saving behaviors. Sixty-nine households from Asahikawa City, Japan, participated in a one-year energy-saving project, reporting monthly actual energy use of electricity, gas, and paraffin oil. Participating households also completed a questionnaire at the beginning, the half-way point, and upon completion of the one-year project. Results showed that intrinsic motivation such as enjoyment and interest impacted both self-reported and actual energy use. Moreover, intrinsic motivation at 6 months had an effect on behavior at one year. Meanwhile, extrinsic motivation, provided in the form of points, failed to impact behaviors, although extrinsic motivation at 6 months affected intrinsic motivation at one year. The role of extrinsic motivation as initial participation encouragement, and the effect of intrinsic motivations on long-term behavior are discussed.