A Bin Method for Calculating Energy Conservation Retrofit Savings in Commercial Buildings

Abstract

The calculation of measured energy savings from energy conservation retrofits is an important step in the verification of the success of a retrofit (Claridge et al. 1992). Several methods for calculating the savings from energy conservation retrofits to HVAC systems in the LoanSTAR program have been proposed, including linear and change-point linear empirical models and calibrated simulation models. Simple least squares linear regression is easiest to use and understand, but is incapable of describing non-linear temperature dependencies of a building's energy use. Change-point linear models are more complex than the simple linear regression and cover a broader range of buildings. However, there are some buildings for which change-point linear models do not fit the data adequately. This paper presents a first look at an hourly bin method for calculating energy savings from energy conservation retrofits to HVAC systems based on hourly whole-building electricity, sub-metered motor control center use and thermal energy measurements. A general procedure for determining the appropriate number of bins is described and the bin method is applied to data from several agencies participating in the LoanSTAR program. Results are compared to existing savings calculation procedures for two buildings.