Abstract: Under market environments, electric customers are offered choices to manage and pay for their electricity usage corresponding to the wholesale market price; this can be referred to as demand response. This paper presents a framework for demand response of commercial buildings, particularly applies to the pumping systems of tall (high) buildings. The problem is to control the pumping systems in response to the market price to minimize the electricity charge. The idea is to utilize the water reservoirs on the top as energy storage devices to manage the electricity consumed by the pumping system from on-peak to off-peak hours, at the same time, maintains water level enough for the demand. The problem is formulated and solved by dynamic programming method. Then, it is tested in a case study assuming markets for real-time pricing.