1. A method of performing analysis of energy consumption for a portfolio of buildings using multi-step statistical modeling, comprising: receiving energy consumption data associated with a building; receiving building characteristic data associated with the building; receiving building operation and activities data associated with the building; receiving weather data; fitting said energy consumption data, said building characteristic data, said building operation and activities data, and said weather data to generate a variable based degree model; determining a base load factor, a heating coefficient and a cooling coefficient associated with the building and an error term from the variable based degree model; generating a plurality of multivariate regression models based on the base load factor, the heating coefficient, the cooling coefficient and the building characteristic data; generating a time series model for the error term to model seasonal factors which reflect monthly dependence on energy use and an auto-regressive integrated moving average model (ARIMA) which reflects temporal dependent patterns of the energy use; and generating a performance score associated with energy consumption for base load of the building, a performance score associated with energy consumption for cooling the building, or a performance score associated with energy consumption for heating the building, or combinations thereof, based on the generated variable based degree model and the multivariate regression models.