Commercial buildings increasingly include technologies capable of providing ancillary services to electric power grids. Features include thermal energy storage inherent in building structures that can be coupled to electric grids through heating, ventilating, and air-conditioning (HVAC) systems controlled by variable-speed drives (VSDs). In parking garages, plug-in electric vehicles (PEVs) are connected to the building power lines through charging stations and can be utilized as grid storage. System power electronics can control equipment power demand at frequencies associated with ancillary services procured in electricity markets, where services dispatch over time scales ranging from hours to seconds. Limitations in provision of services by buildings include building-scale thermal and electrical energy storage capacities: thermal comfort of occupants, state of charge of PEV batteries, and the power rating of VSDs and PEV chargers. This paper reviews available technologies and necessary control strategies for HVAC systems in commercial buildings to provide ancillary services. We then develop physically-based scaling metrics for building thermal storage technologies accessible through HVAC systems. In addition, the effect of ancillary services provided by HVAC systems on grid network and electricity market operations is analyzed using simulation case studies, incorporating magnitude scaling of services. We finally evaluate a possibility that the HVAC systems and PEVs provide three-phase voltage and power balance regulation services, respectively.