The heating, ventilating and air-conditioning (HVAC) systems of large commercial office buildings consume a significant amount of electric power. Instead of passively consuming energy, these systems can provide frequency regulation (FR) services to the electric grid by adjusting the power consumption in response to a signal sent by the electric grid operator. This paper has four primary goals: First, it provides the theoretical support and states the need for using HVAC systems to provide FR. Second, it proposes two methods of using HVAC systems for providing FR - a direct method and an indirect method; these two methods are developed as models and tested in simulation. Third, it addresses the challenges of using commercial building HVAC systems for FR; this motivates the development of a new supervisory control method to support the HVAC system for providing FR service. Fourth, it evaluates the simulated results based on the performance based regulation (PBR) rules proposed by the PJM regional transmission organization; thus, it provides the reference for the future field-testing (C) 2013 Elsevier B.V. All rights reserved.