A multi-mode thermostat includes a sensor of ambient temperature and control circuits coupled to the sensor, wherein the control circuits are responsive to signals from the sensor to maintain a predetermined regional temperature. First electrically actuated backup circuits are responsive to a firt sensed operational power level to alter a status signal transmission rate by the control circuits. Second electrically actuated backup circuits are responsive to a lower sensed operational power level to provide a backup, lower regional temperature electromechanically.