The annual performance of two full-size integrated collector/storage solar water heaters (ICSSWH) was experimentally determined. The ICSSWHs incorporated a novel heat retaining storage vessel and employed a new technique for the construction and assembly of the encompassing collector unit. Systems A and B were respectively a 1.5 m long ICSSWH unit partially enclosed within the reflector sections and a 1.0 m long ICSSWH unit fully enclosed within the reflector sections. Details of the annual measured performance of the two designs are presented in this paper. (C) 2001 Elsevier Science Ltd. All rights reserved.