Water-flow window can reduce indoor cooling load from direct solar radiation and preheat domestic hot water at the same time. It is quite suitable for hospital with patient wards and large demand of hot water, especially buildings with large area of glazing curtain-wall. Field measurement was carried out during July 2018 at a major comprehensive hospital in Shenzhen, and the inner surface of the four-storey west-facing glazing curtain-wall reached over 45.6oC in the daytime. The year-round energy-saving potential is investigated by applying water-flow window to the curtain-wall through programme simulation, with a pre-validated FORTRAN programme. The results show that the year-round solar energy utilization rate can reach as high as 9.4%, and the indoor thermal environment is better, compared with conventional window design. The preheated water can be used in wards for showering and help building energy conservation. Water-flow window has great potential for large-scale application within similar buildings.