The operational consequences resulting from the combination of a flexibly operated combined heat and power unit (CHP) and an off-grid biomethane filling station at one biogas plant were investigated. Four different operating scenarios were compared to evaluate the storage capacity needed to balance biogas demand fluctuations and biogas production. The scenario in which fuel production was given priority and electricity was produced within the remaining hours proved to cause the lowest additional costs since it does not require additional installation of biogas storage capacity and causes minor opportunity cost in electricity marketing. Giving fuel demand the priority reduces the necessary biogas storage capacity by 75 % compared to parallel optimization of the electricity and fuel demands.