The obfective of this study was to conduct the energy analysis of a lignite-fired fluidized-bed boiler with the capacity of 3 ton/hr of steam rate. The boiler was designed and fabricated in Thailand. Energy analyses based on the first and second laws of thermodynamics were conducted. Results show that the boiler efficiencies based on first law and second law were 73.5-75.4% and 23.2-23.8% respectively. Mathematical modeling was also carried out to predict the boilers performance under various loads. The first law efficiency of the prototype fluidized-bed boiler was 3% higher than that of the commercial boiler imported from China. It may be concluded that the Thai designed boiler had a good efficiency and an acceptable performance standard of the conventional fluidized-bed boilers.