Abstract: A sun operated installation for heating liquids generally comprises a collector of insolation and a storage tank. The collector and the tank are interconnected by a circulation pipe. In that pipe are provided two inlet openings, one in the upper and one in the lower part of the storage tank. The upper opening is larger than the lower one. In consequence the liquid in the upper part of the tank is heated earlier than that in the lower part. Installations of that type are destined primarily, but not exclusively to heating water for use in domestic establishments.