This paper reports on the electrical system design and development of Home Energy Management System (HEMS) of a solar house, named "Omotenashi House", which was entered in the Solar Decathlon Europe 2012 (SDE2012). Completed solar houses were judged on a number of factors; in particular, the electrical energy balance, and whether it is possible to achieve comfort conditions along with normal house functioning using electrical power generated solely from the solar panels. Therefore, it was necessary to use efficient battery storage for electrical power at night, as well as modern energy-saving home electrics, appliances, and electronics, and high-performance thermal insulation from vacuum panels. Sensors monitored temperature, humidity, light quality, and other factors to measure the comfort conditions. We decided the requirements of the electrical system and HEMS for SDE2012, and we planned the electrical system and HEMS. The test process and schematic diagrams and hardware and software components were explained in figures and tables. The solar house we constructed at SDE2012 did not perform to our expectations because of some electrical problems, but HEMS functionality was verified. In Japan, standardization of HEMS is proceeding due to the Echonet Consortium, a group of Japanese electronics manufacturers. (C) 2014 Elsevier B.V. All rights reserved.