1. A building management system comprising: one or more sensors configured to measure one or more predictor variables for potential use in a baseline energy usage model for a building; and a baseline model generator comprising a processing circuit configured to: receive an initial set of predictor variables including the one or more measured predictor variables; generate a first set of coefficients for the baseline energy usage model based on the initial set of predictor variables; remove one of the predictor variables from the initial set of predictor variables to create a subset of the initial set of predictor variables; generate a second set of coefficients for the baseline energy usage model based on the subset of the initial set of predictor variables; calculate a test statistic for the removed variable using a difference between the first set of coefficients and the second set of coefficients; and automatically select the removed predictor variable for use in the baseline energy usage model in response to the test statistic exceeding a critical value.