This paper discusses heat pump room air conditioners and their new techniques in Japan. The variable capacity system, using a gas injection and release compressor, has an energy savings of 15 percent, as compared with conventional systems. The compressor system does not need either a starting relay or a starting capacitor in the electrical circuit. Energy savings can be achieved for the following reasons: (1) The system has a two-stage heating capacity without an electric heater: high heating capacity at low outdoor temperatures and low heating capacity at high outdoor temperatures. (2) The ratio of heating to cooling capacity of the system is more than 1.5, which is considered to be adequate far Japanese climates. (3) A smaller compressor motor can be utilized in the system.