A method of monitoring HVAC usage includes: maintaining a data structure in an on board memory of a programmable usage monitoring HVAC thermostat; receiving an initiation signal from a relay; receiving a termination signal from the relay; and updating the data structure by adding a duration in units of time to an accumulated time associated with the relay to keep a log of the elapsed time a function associated with the relay was operative. A programmable usage monitoring HVAC thermostat comprising, a user interface; a microprocessor coupled to the user interface; and a firmware upgradeable memory coupled to the microprocessor.