Systems and techniques are provided for automatic security system mode selection. A set of signals may be received from sensors distributed in an environment with a security system. The security system may be in a first mode. An occupancy model may be received. An occupancy estimate may be generated for the environment based on the set of signals from the sensors and the occupancy model. Mode rules may be received. The mode rules associate occupancy estimates with modes of the security system. A second mode for the security system may be determined based on the occupancy estimate and mode rules. The second mode may be different from the first mode. The mode of the security system may be automatically changed from the first mode to the second mode.