The cooling system represents a significant opportunity for improving efficiency. In many cases, relatively simple and inexpensive changes, such as improving room sealing, moving cables or other objects that obstruct airflow or installing blanking panels, can pay immediate dividends. In addition, new technologies, such as variable capacity room air conditioners and sophisticated control systems, should be considered for their impact on efficiency. Finally, supplemental cooling systems provide a response to increased equipment densities that can increase the scalability and efficiency of existing cooling systems.