Trigeneration plant also known as combined cooling, heat, and power, offers an efficient approach in producing multiple energy products while reducing environmental emission and energy losses. It consists of cascaded processes which are interdependent in terms of the interconnectivity of materials and energy flow with each other. The design of such systems requires a methodology which considers multiple-objective goals such as maximizing economic performance and product plant output, and minimizing environmental emissions. Hence, this study proposes a fuzzy linear programming approach in the optimal design of a trigeneration plant. Since, the price of energy products have shown to have price fluctuations, the product price variability should be a key component in the design of a trigeneration plant. Limited studies have been conducted on the optimal design of a trigeneration plant where product price variability with respect to the plant capacity was considered. This study showcases the feasible optimal plant capacity given the price variability of the trigeneration products. Results revealed the feasible optimal capacities of each of the components of the trigeneration plant within the price variability change. The results of the study will aid plant owners and engineers in designing a trigeneration plant based on price fluctuation range of various energy products.