This study presents a one-dimensional mathematical model for simulating the transient processes of sheet and tube type photovoltaic/thermal (PV/T) system and conventional type solar collectors. The models are based on the energy conservation for the glass cover, PV plate, absorber plate, tube, water in the tube and storage tank for the PV/T and the same layers excluding PV plate in conventional solar collector. The models were all first order ordinary differential equations which could be easily solved in the Matlab computer program using ode solvers. For the purpose of validating the proposed methods, performance tests were done on the both systems. Satisfactory convergences were found between the measured data and calculated results. The statistical analysis was performed for the scientific validation of the results. The current model is suitable for the single cover tube type PV/T systems. (c) 2012 Elsevier B.V. All rights reserved.