As the major thermal source, boiler system consumes a large amount of energy for both industrial and commercial use. A well operated boiler system with higher efficiency is essential for the system performance. However, in practice, due to various reasons such as the outdated system control method, oversized boilers, improper boiler operation schedule and system settings, the existing operation of the boiler system not only increases the system energy consumption but also lead to much higher CO₂ emission. This paper presents a case study that was conducted for an industrial boiler system to assess the system performance while identifying opportunities to increase the system energy efficiency. First, the paper discusses the system improvement opportunities for the exiting boiler system, such as resetting the system steam pressure lower, installing VFDs to the FD fans, optimizing the multi-burner use pattern, optimizing the feed water system. In particular, single burner mode was investigated with air/fuel ratio adjusted to the optimum level. In addition, the paper provides a brief energy analysis after developing optimized single burner mode operation. It showed that with optimized burner operation, up to 7% fuel usage was saved at lower load condition.