A development of biomass cogeneration facilities business comes with many challenges such as operational compliance and budget constraints. Maintenance cost is often oppressing some portion of the annual budget. Apparent outage costs due to loss of production during planned operation and maintenance are crucial. It requires a strategic maintenance framework to ensure optimum performance of the biomass cogeneration business. This paper presents a Mix Integer Linear Programming optimization model for the palm oil mill-based cogeneration facility considering fuel cost, electricity cost, maintenance duration and maintenance interval. The model aims to minimize total annual operation costs to ensure tenants can depend on reliable, uninterrupted heat as they deserved from the heat supplier. The sensitivity analysis results determine the lowest annualised cost had impacted by lower fuel and outsource electricity costs, six days maintenance duration, and 1.1 maintenance intervals.