Systems, methods, and medium remotely monitor and control heating, ventilation and air-conditioning (HVAC) units. The method includes receiving by a processor via a communication network supply temperature data indicating a supply air temperature in a duct coupled to an HVAC unit. The method includes receiving by the processor via the communication network zone temperature data of a space being maintained by the HVAC unit. The method includes receiving by the processor via the communication network thermostat data from a thermostat in the space and analyzing by the processor at least one of the supply temperature data, the zone temperature data and thermostat data. The method includes generating by the processor a control signal responsive to the analysis and transmitting via the communication network the control signal to an HVAC controller, wherein the control signal causes the HVAC controller to control the HVAC unit.