Detailed end-use models are increasingly popular for forecasting energy requirements for electric utility systems. This paper describes an extension of the end-use approach to demand forecasting and loadshape analysis. In the approach a clear distincting between the pattern of usage and the level of usage is made. The pattern of usage for a particular end-use is defined by a sequence of use factors. For weather insensitive end-uses, the use factors are functions of time (i. e., time of day, day type, and month); while for the weather sensitive end-uses, they are functions of time as well as a camposite weather variable. The model structure has been implemented successfully for a number of utilities to analyze and simulate system loadshapes under different assumptions.