A method and system can provide building energy performance metrics that can help identify specific zones within a building which may have energy efficiency problems. The method and system can collect data from: indoor temperature sensors and humidity sensors present in each zone of a building; one or more temperature sensors and humidity sensors present outside of the building; one or more utility meters; and one or more HVAC devices. This data from the sensors can be aggregated and formed into a first profile. The energy efficiency calculation system can analyze the first profile to provide various energy performance metrics which can include, but are not limited to, energy efficiency ratios for air conditioners, the R-value or thermal resistance of the building, an amount of heat loss for the building, energy consumption by the building, current HVAC performance parameters, and utility usage comparisons.