This paper discusses two important aspects in achieving better building energy performance, with particular reference to large air conditioned buildings in Hong Kong . The first one is the application of Demand Side Management (DSM) strategies in buildings in Hong Kong. The current status of electricity supply and barrier to applying DSM in buildings are reviewed, and the short-term actions in buildings' DSM are suggested. The second is to establish suitable performance indicators for building energy consumption. The needs for better indicators of energy utilization performance in existing buildings. A new indicator for building air conditioning energy performance is proposed.