###### Abstract  
The exploitation of solar irradiation in the building sector is a promising way to achieve decarbonization and reduce the operating costs of the building. The potential of solar energy in Greece is high and therefore this idea can lead to excellent results. In this direction, the goal of the present analysis is the detailed investigation of different solar thermal systems for domestic hot water production in the different climate zones of Greece. Four typical cities are studied in order to examine the climate zones A, B, C, and D, while three different solar thermal collectors coupled to insulated storage tanks are studied for every city. The simple flat plate collector, the advanced flat plate collector, and the evacuated tube collector are the selected solar systems for the present work. The climate data and the characteristics of the solar thermal systems follow the Greek Chamber regulations known as \"KENAK\". The analysis is conducted by following the well-known f-chart method and every design is optimized by using energy and financial criteria. The final design is determined by conducting a multi-objective evaluation methodology. It is notable to state that the collector slope and the collecting area are important parameters of this work, while the study case regards a building with 30 residents. According to the final results, the advanced flat plate collector is the best choice according to the multi-objective evaluation procedure. solar thermal energy; flat plate collector; evacuated tube collector; optimization; f-chart +
Footnote †: journal: _Sci._  
0000-0002-4000-0000-0000-0000-0000-0000-0000-0000-0000-0000-0000-00000-00  
with a collecting area of around 2-2.5 m\({}^{2}\) and a tank of 150-200 L [9]. However, these are general rules and there is a need for more accurate design, especially in greater buildings and in central systems with many residents. Regarding, the solar collector types, the use of a flat plate collector (FPC) is the most usual choice [10], while the selection of an evacuated tube collector (ETC is an alternative, especially in cold regions [11]. In the domain of storage tanks, sensible heat storage is the most usual choice [12], while there are ideas about using latent storage with phase change materials [13]. Moreover, it is useful to state that another idea is the incorporation of the tank inside the collector [14]; a compact design that has lower efficiency than conventional systems. Last but not least, solar thermal technologies can be combined with heat pumps for producing DHW [15]. Greece is a country with a high solar potential which is estimated at 1750 kWh/m\({}^{2}\)[16] for a 45\({}^{\circ}\) tilted surface in Athens, while similar values are obtained for other locations. Moreover, Greece is a country where the utilization of solar thermal systems for building applications is a socially acceptable technology [17] with social and environmental benefits [18], so the further installation of solar thermal systems in Greece is something that is feasible. Moreover, [PERSON] and [PERSON] [19] conducted a study based on a 30-year experience with solar thermal units and they found that there is an important reduction in CO\({}_{2}\) emissions due to the solar irradiation exploitation in Greece. In another work, [PERSON] and [PERSON] [20] stated that the environmental impact during the construction of the solar thermal collectors is relatively low and so the life cycle assessment is positive. Furthermore, they concluded that the payback period has an acceptable value of close to 5 years. Another environmental work about the solar thermal systems in Greece by [PERSON] et al. [21] shows that the initial materials and the construction techniques of these systems have a low impact on the overall system's environmental performance. Thus, the energy analysis of the solar thermal systems is the critical factor that determines both their energy and their environmental characterization of them. In this direction, [PERSON] et al.