Designing a biomass combined heat and power (CHP) system that fulfils uncertain energy demands is a challenging task. This task becomes increasingly complex when historical data and probability distributions are not well defined. This work presents a newly developed decision analysis design framework for biomass CHP system which considers three types of decision-makers, namely optimistic, pessimistic and cautious decision-makers. To illustrate the proposed framework, a palm-based biomass CHP case study is solved. In addition, sensitivity analysis is performed to evaluate the effect of Feed-in Tariff (FiT) rates towards the design of CHP system. The optimum biomass CHP design is then further analysed to determine the “must-have”, “optional” and “must-avoid” equipment within a given range of power demand. The proposed decision analysis design framework enables decision makers to make informed decisions.