1. Apparatus for estimating energy usage of two or more electrical devices, the apparatus comprising: means for receiving usage profile data for at least first and second electrical devices, with the first and second electrical devices having different load ratings; means, responsive to an aggregate energy usage value based at least on energy usage of the first and second devices, and responsive to the usage profile data for the first and second electrical devices, for estimating electrical usage of each of the first and second devices, wherein the means includes a Bayesian estimator.