In order to investigate the performance of air-to-air heat pumps for residential heating in the Black Sea region of Turkey, an experimental set-up was constructed. An electrically driven air-to-air heat pump was used for heating a laboratory building with a floor of 75 m2. In this study, a high-efficiency air-to-air residential heat pump was instrumented and tested in the heating mode under laboratory conditions. The coefficient of performance and heating capacity of the system were measured during steady-state, dehumidifying, and frosting/defrosting conditions. The study encompassed an evaluation of system and component performance for ambient temperature levels between 10 and -4.0-degrees-C and for discrete relative-humidity levels ranging from 65 to 80%.