The article discusses biogas technology as an important direction in renewable energy. To improve its efficiency, it is necessary to choose a biogas plant with optimal parameters at the design stages. Insufficient research requires the development of a methodology that would take into account climatic conditions and operating modes of biogas plants. In the process of processing, the most energy-intensive is the heating of biomass in the bioreactor to the required fermentation temperature and to compensate for heat losses. At the same time, it is important to distinguish between start-up and steady-state modes of operation of biogas plants. The required power is influenced by the biomass loading condition. In a continuous or intermittent process of loading biomass, the required power will differ and subsequently will affect the choice of the heater in terms of power. To assess the effect of different modes of operation of biogas plants on the required power for heating biomass, an indicator was introduced that takes into account the ratio of the starting power to the power of the steady state. In the course of the study, a 100 m3 reactor with various internal and external design and operating parameters was considered as an example. As a result of the study, a number of important conclusions were made: the heating capacity of a biogas plant in a mesophilic mode with continuous and periodic processes and in a thermophilic mode with a periodic process is determined by the start-up mode; for a thermophilic mode with a continuous operation of a biogas plant, the heating power is in a steady state; in the mesophilic mode with a continuous process, the reactor loading by 70% or 90% affects the choice of heating power to a lesser extent than the ambient temperature; In a thermophilic mode with a continuous process, the ratio of powers with an increase in the thickness of the thermal insulation of the reactor has almost the same, in terms of values, a descending character for the options for loading the reactor by 70% or 90% and for the considered ranges of ambient temperatures (+ 300C to -300C). A comprehensive methodology for the design of a biogas plant will determine the optimal parameters to improve its efficiency.