The California Energy Commission is proposing the requirement of programmable communicating thermostats (PCTs) in the 2008 Revision of Title 24 residential building codes.  PCTs are a DR-enabling technology that can reduce a home's A/C consumption upon receiving a price message or curtailment command.  Policy makers envision PCTs installed statewide to provide demand relief as an alternative to rolling blackouts on peak consumption days when generation capacity cannot meet the power demand. Theoretically, a network of PCT enhanced homes could provide a large amount of load reduction, but the precise system response is unknown and could result in instability. We simulated a large group of PCT houses with random thermal properties in order to study the system's open loop response, stability, and response under feedback control. To date, we have examined on-command load reductions using various curtailment start and exit techniques.