A method of and system for auditing the energy-usage by a facility, where the facility includes an energy-using system having an operating parameter with a value. One embodiment of the method includes acquiring an initial value of the operating parameter, acquiring initial data of the energy-using system with the operating parameter set at the initial value, acquiring values relating to a weather parameter for the facility, and creating a baseline model of the energy-usage by the facility with the initial energy-using system data and the weather data. Some embodiments of the method can further include determining an initial rate of energy-usage by the facility based upon the baseline energy model, changing the initial value of the operating parameter, determining a modified rate of energy-usage by the facility, and calculating a savings in energy costs from changing the initial value of the operating parameter.