A commissioning unit with an energy management system (EMS) was developed to be used together with facility monitoring and control systems (FMCS). This paper describes the testing of the new coupling system, in which a detailed management program is embedded for real time control decision making. First, a survey was conducted to evaluate the current power consumption of the facility systems, and found that HVAC is the most energy intensive system. Then a case study was performed, while the plant was in operation, to demonstrate the feasibility of the new coupling system, and a 9.6% chiller efficiency increase and total 23.2% annual energy saving for the chillers were reached, by optimizing the part load ratio condition of chillers and pumps. The results from in situ experiments show that applying this energy management system to the IT industry is feasible. A better custom-made FMCS with EMS, and full scale testing to greatly increase the overall energy efficiency, is recommended. (C) 2011 Elsevier Ltd All rights reserved.