Current research has highlighted three major gaps in the literature: (a) a rarity of studies on photovoltaic thermal systems with channel boxes, (b) a lack of data on pressure drop and surface temperature distribution in these systems, and (c) absence of analysis regarding the impact of materials (metals and polymers) used in photovoltaic thermal systems on performance, cost, payback time and weight. The novelty of this paper lies in addressing these gaps by studying a new channel-box photovoltaic thermal system, varying the number of channels and the height of the collectors that distribute water to these channels, in order to identify the most efficient design in terms of electrical, and thermal efficiency as well as pressure drop. In addition, the impact of different heat exchanger materials (metals and polymers) on the performance, cost, payback time, and weight of photovoltaic thermal systems was investigated. 3D numerical simulations were carried out using COMSOL Multiphysics software, based on the finite element method, and validated by outdoor experimental research. The results show that the photovoltaic thermal system 8 design performs best, with a total efficiency of 89.42%. In addition, the aluminum photovoltaic thermal system stands out as the most cost-effective option, with a payback time of 0.823 y (300 d) and annual savings of $459.262, while being 38% lighter than the copper system. Based on this study, it is recommended that the photovoltaic thermal system 8 be implemented because of its exceptional performance and ease of implementation.