A system that allows a contractor to remotely monitor and/or interact with its customers' building control systems, such as heating, ventilating and air conditioning (HVAC) systems, and analyze information obtained from the building control systems over time. Such a system may help the contractor monitor and diagnosis customer building control systems, setup service calls, achieve better customer relations, create more effective marketing opportunities, as well as other functions. In some cases, the disclosed system may help a contractor pro-actively identify possible issues with its customer's building control systems, and only then schedule maintenance as required. In some cases, based on the analysis of information obtained from the building control systems over time, the system may output indications of abnormalities in the operation of the building control systems from which information may be received.