Abstract: The applications of solar hot water systems in buildings worldwide were introduced. The problems with the systems were presented in the aspects of technology and installation. Some suggestions were offered from foreign experiences, such as improving the technical and industrial levels of solar hot water systems, strengthening the construction of the technical institutional system, developing the national or local regulatory rules for mandatory installation of solar hot water systems in buildings, and encouraging the application and promotion of solar thermal technology. 

Key words: solar energy; water heating system; energysaving and carbon emission reduction