To cope with environmental and energy issues, the automobile industry has developed and started the mass production of electric, hybrid and fuel-cell vehicles. Air conditioners for these types of vehicles need to be highly efficient and need to be operable even when the engine is off or when installed in solely battery-powered vehicles. In response to these needs, we have developed small, light-weight, high-efficiency electric compressors and inverters. With respect to the compressor, taking account of the requirements for in-vehicle use, we have developed a structure with extremely good heat and vibration resistance. With the use of acoustic mode analyses and other approaches, we have developed lower-vibration, lower-noise compressors that will ensure a comfortable environment within the vehicle even when the engine is off. With respect to the inverter, we have, together with automakers, streamlined the use of components such as power electronics components, heat sinks and noise filters, and halved the dimensions via the introduction of new types of circuits, including the charging circuit. This article describes the technological development process of our electrically powered compressor.