This paper reports the results of a project to install, operate, and evaluate a prototype solar energy system. The system is intended to reduce conventional energy consumption in satisfying space heating and domestic hot water requirements for a single-family residence.The operational test period consisted of one heating season from November 1, 1979 through March 31, 1980. During this period, the building was occupied for four consecutive months. The system is located in a building in New Castle, Pennsylvania.