Abstract: An energy demand controller having a sensor for measuring the instantaneous power being delivered to a building, a thumb wheel switch for preselecting a power limit for use in the building, and circuitry for comparing the instantaneous power to the power limit and to switch off power to various heating zones within the building in order to maintain the instantaneous power below the preselected power limit. The control circuitry includes a cycling circuit only operative when the instantaneous power exceeds the measured power to deactivate a sufficient number of heater circuits in order to drop the instantaneous power below the preselected power limit for a predetermined time interval only. At the end of the predetermined time period, the deactivated heater circuits are turned back on. If the instantaneous power still exceeds the preselected power limit, then other zone heaters of sufficient number are likewise deactivated in a second predetermined time interval.