This disclosure relates to methods, systems, and devices for detecting an operational mode of a building component of an environmental control system. In some instances, the apparatus may include a sensor for outputting a signal related to a measure of power drawn by the building component. The sensor may be a current sensor associated with a power cord of an air conditioning unit. The signal output by the sensor may be received by a signal conditioning circuit for conditioning the signal received from the sensor such as, for example, by amplifying and/or filtering. A comparator may be configured to compare the conditioned signal to a specified threshold associated with an ON condition and/or an OFF condition of the building component. The apparatus may include a wireless interface configured to wirelessly transmit a determination of whether the building component is ON or OFF based on the result determined by the comparator.