In this paper, the energy balance equations for the different components of hybrid photovoltaic thermal integrated-biogas plant have been written for quasi-steady state conditions to develop a thermal model. An analytical expression for slurry temperature has been obtained as a function of design and climatic parameters namely mass of the slurry, mass flow rate of fluid in collector, number of collectors, solar intensity, ambient temperature etc. Numerical computations have been carried out for climatic conditions of Srinagar, India. Based on mathematical computations it has been observed that the optimum slurry temperature (∼37°C) is achieved for a given set of design parameters of biogas plant and hybrid collectors (MS = 2000, \(\dot m_f = 0.05 kg/s\), L = 25 m). It is also observed that the peak slurry temperature decreases with increase in mass of the slurry as expected. Equivalent CO2 credits earned by hybrid biogas plant for optimised parameters have also been evaluated.