Abstract: The HVAC condition based maintenance system and method provides for a system to reduce operating costs by replacing existing time based scheduled maintenance with an on-condition based maintenance system and method for continuous monitoring and acquiring condition based data from an operating HVAC system, transmitting data to a remote server for storage, analysis and trending, recognizing operational performance reductions based on the comparison of current trending to historical data, and for triggering notification of failures and corrective action based on routine, impending and immediate problem recognition. Additionally, the acquired data is used to derive actual heat load characteristic of the building, identify HVAC system deficiencies, building deficiencies and installation issues and load imbalance of multi-unit systems providing direction for system improvements.