1. A data processing system, comprising: an energy management service unit that is configured to be coupled to a plurality of energy management devices located at a plurality of sites; wherein the energy management service unit is configured to cause collection of energy usage data from the plurality of energy management devices located at a plurality of sites, and to store the energy usage data; a computer-readable storage medium coupled to the energy management service unit and storing one or more sequences of instructions which, when executed by one or more processors, cause the one or more processors to store a plurality of site groupings, to operate a management interface configured to receive requests for statistical views of particular energy usage data associated with one or more of the plurality of site groupings, and to generate and cause display of the requested statistical views on a computer display unit.