1. A monitoring system for a heating, ventilation, and air conditioning (HVAC) system of a building, the monitoring system comprising: a monitoring device installed at the building, wherein the monitoring device is configured to (i) measure an aggregate current supplied to a plurality of components of the HVAC system over a series of time periods, (ii) process the aggregate current data for each time period to create a frequency domain representation for each time period, and (iii) transmit, for each time period, the frequency domain representation based on the measured aggregate current; and a server located remotely from the building, wherein the server is configured to (i) receive the transmitted frequency domain representations, (ii) based on the received frequency domain representations, assess whether a failure has occurred in a first component of the plurality of components of the HVAC system, (iii) based on the received frequency domain representations, assess whether a failure has occurred in a second component of the plurality of components of the HVAC system, (iv) generate an alert in response to determining presence of a fault of either the first component or the second component, and (v) send the alert to at least one of (a) an owner of the building and (b) an HVAC contractor.