A layer poultry farm that produces commercial eggs discharges wastewater from the manure washing process, which is collected in a plastic sheet covered lagoon and used to generate biogas through an anaerobic digestion process. This paper proposes a biogas power plant design for a case study of a 100,000 layers cage farm to meet the power demand and electricity requirement, considering both technical and financial analysis. The potential in biogas production is determined using mathematical models and constraints based on a previous similar research technology. The gas engine and generator converting biogas to electricity are sized based on the collecting data of currently peak power demand, electricity requirement and estimate to the full-scale production of the farm. The initial investment as the major component cost is obtained from the supplier bill of quotations and the annual expense is estimated by the maintenance cost of time of operation leading to achieve the financial parameters. The result shows the range of energy production based on the number of operating cage houses in the farm, supporting 44% of the energy requirement. To maximize the benefit, the power plant is programmed to support all power demand during the daytime, known as the on-peak period which is charged with the highest tariff rate. The financial analysis is recognized by its positive Net Present Value (NPV), the higher Internal Rate of Return (IRR) than expected return rate, and the lower Levelized Cost of Energy (LCOE) than the electricity cost charged by the utility.