The utility bill analysis screen in REM allow the user to enter in monthly utility bill data for two fuel types in which REM will disaggregate the utility bills into the common end-uses (heating, cooling, water heating, baseload).  Based on the fuel types entered, REM will utilize a variable degree day regression or multivariate regression to determine the heating and cooling loads.  Water heating and baseloads are derived from the utility bills or by calculated estimations from entered data in the utility bill screen.  

The utility bills can be saved into a building file before any building information is entered.   A user can view the disaggregated utility bills without any building data.  Once a building is entered into REM, then the REM simulation results are posted next to the weather normalized utility bills.  This can allow the user to tune (calibrate) the REM building file so that the results match up closely with the utility bill disaggregated results.  

There can be situations where the utility bills show no correlation to monthly weather data and the results may not seem intuitive.  As an example, if the gas utility bills show very little variance throughout the year but the degree days indicate a very cold winter, REM regressions may not calculate a correlatioan and results may seem strange.  The home may be either super insulated, or the furnace was not really working or on in reality so REM cannot determine the end-use consumption accurately.