The rapid increase in the share of renewable energy sources within the Unified Power System of Ukraine necessitates the integration of high-flexibility energy storage systems to compensate for their inherent variability. However, the implementation of battery-based storage systems significantly raises the overall cost of the energy infrastructure, complicating investment decisions for potential consumers. Key drivers stimulating the deployment of renewable energy include the pursuit of energy independence, improved reliability, ownership of generation assets, and the escalating and volatile costs of electricity supplied by centralized systems. This study proposes the utilization of biogas plants as high-maneuverability energy storage units. It is envisaged to leverage existing gas transportation and distribution networks for the accumulation and storage of biomethane. At the initial stage, biomethane is intended to be exported to EU countries, with production targets set to reach 8 billion m³ and beyond. According to the Bioenergy Association of Ukraine (UABIO), economic viability is typically achieved by biomethane plants with an annual production capacity of at least 3 million m³. A critical factor influencing the decision-making process for small and medium-sized biogas plant operators is the availability of predictive data on the energy efficiency of the proposed decentralized energy supply system in comparison with existing centralized alternatives. In this work, the assessment of energy efficiency indicators is conducted through an analysis of the share of renewable energy utilization, the type and cost of energy derived from both renewable and centralized sources. Given the capability of biogas plants to produce multiple forms of energy (electric, thermal, mechanical, etc.), it is recommended to consider both the share and the total volume of these energy types when designing the system. The proposed methodological approach is advised for use during the technical specification development phase, as it provides a rationale for investment decisions regarding the construction or modernization of energy supply systems.