This paper presents the comparative study of two commercially available types of solar water heaters for domestic applications: Flat Plate Thermosyphonic Units (FPTU) and Integrated Collector Storage (ICS) solar water heaters. The conducted analysis initially focuses on the experimental investigation of the thermal behaviour and proceeds to the detailed holistic environmental analysis for both systems through a completed Life Cycle Assessment (LCA) study (i.e. throughout their fabrication, installation and operation phases). The energy performance of the systems (studied in three different geographical regions) proved that both technologies perform more than effectively, with the FPTU system being more efficient regarding the heat retention of the stored water, while the ICS systems presented higher time response in the temperature increase. On the other hand, the LCA results imply that the FPTU systems are less environmentally friendly compared to their ICS counterparts mainly during their fabrication and installation phases. (C) 2017 Elsevier Ltd. All rights reserved.