Occupancy-based controls in residential buildings can save energy by adjusting HVAC systems when no one is home. Two types of controls, reactive and predictive, were compared in a simulation of a 27-home community in Basalt, Colorado. Results showed that using these controls can reduce HVAC energy use by 1%-20% compared to not using them. The amount of energy saved depends on how often people are in the building and how much the temperature is adjusted when they're away.