1. A method for determining an uncertainty in parameters of a building energy use model, the method comprising: receiving an energy use model for a building site, the energy use model having one or more model parameters, wherein the energy use model is used to predict an energy consumption of the building site as a function of the one or more model parameters and one or more predictor variables; calculating a gradient of an output of the energy use model with respect to the model parameters; determining a covariance matrix using the calculated gradient; and using the covariance matrix to identify an uncertainty of the model parameters.