The case study facility is a shopping mall with a total floor area of 112,000 square meter (1,200,000 square feet). A central plant in the mall is equipped with dual-fuel generators, turbine engine chillers and boilers as well as absorption chillers. The central plant provides electricity to most mall tenants, and chilled water and heating water to HVAC systems in the entire mall. The rest of the electricity is provided by a local utility company. Continuous Commissioning was applied to solve existing facility problems, to optimize facility operation, and to reduce operational costs. The cause of a persistent major comfort problem was identified. A costly retrofit with a total value of $50,000 was avoided. The key system performances were tested and measured. Based on the actual key system performance, optimal operation and control schedules were developed. The integrated whole facility optimization approach also identified a potential cost reduction of $81,000/yr with a retrofit cost of $58,000. The improved chilled water system operation could potentially reduce annual gas and fuel costs by $60,000. This paper presents methods, analyses, and results of this integrated system optimization study.