In order to consider the potential for electricity supply from a biogas power generation system (BGP) located adjacent to a livestock barn, the power balance was determined by using both simulation and actual measurement. Examination of power balances at the barn and the BGP showed that a certain amount of electricity for supply could be secured based on load leveling in both tie-stall barns and free-stall barns. BGPs are a viable renewable energy (RE) power source that can produce enough electricity for system operation and maintenance as well as a significant surplus of supply for power companies and other users. BGPs have the potential to allow output control appropriate for the relevant amount of gas storage. Further, output control based on the use of a gas holder in combination with changes in the number of biogas generators could allow more efficient usage of biogas. Specifically, the range of power output adjustment can be widened through parallel operation of several biogas generators, instead of a single generator. In other words, one biogas generator uses a constant power supply, and the other uses it to control the output for the related amount of gas storage. In this way, the possibility of achieving a constant electricity output through biogas power generation system and a regulated power supply was demonstrated.