The HVAC Primer describes energy savings opportunities and context for packaged rooftop units (RTUs) for utility energy managers and their trade allies. RTUs are ubiquitous in commercial spaces but are also a difficult market to reach. Analysis shows many opportunities for savings over code for new and existing RTU programs. In addition, utilities that conduct pilot projects or evaluations of their own RTU program measures can leverage the results with a standardized analysis protocol. This will greatly aid in establishing more appropriate program incentives and marketing numbers that will support efficiency activities.