A computer readable medium with instructions stored on the medium. When the instructions are executed by a processor, they cause the processor to calculate overall efficiency. A system for determining the overall efficiency for a building. The system comprises: an environment system controller with a processor used to calculate overall efficiency; a plurality of indoor temperature sensors in communication with the environment system controller; an outdoor temperature sensor in communication with the environment system controller; an efficiency monitoring device in communication with the environment system controller; and a chronograph configured to time stamp sensor readings.