PRISM: measuring savings the easy way

A standardized tool for estimating energy savings from billing data. An easy-to-use software package requiring only readily available data.

The advanced version of PRISM (PRInceton Scorekeeping Method) makes it easy to transform run-of-the-mill billing data into statistically sound savings estimates. With PRISM, utilities and energy analysts can systematically estimate total savings from a conservation or demand-side management program, for large samples of houses or buildings participating in the program, and for comparison groups as well. Enhanced model tuning and data pruning in PRISM produce reliable savings estimates and expanded statistical capabilities, from readily available data.

PRISM, originally released in 1986, and available since 1995 as a Windows-based easy -to-use software package, has been acquired by some 500 organizations, and has become the standardized billing-analysis evaluation method used by utilities, private firms, government agencies, and universities. PRISM has a Windows-based user interface that integrates major statistical functions with numerous user-friendly features. For more information see Publications.

summary of method

PRISM is a statistical procedure that processes a year of monthly billing data from a house or building to produce a weather-adjusted Normalized Annual Consumption (NAC) index, along with other physically meaningful parameters and extensive reliability statistics. A key feature of the method is its estimation of best reference temperature to which heating and cooling degree-days in the model are computed. PRISM is generally run on the pre- and post-weatherization periods for all buildings in a sample to produce distributions of savings across the sample. With PRISM, participant and control groups are easily compared, in graphical and tabular forms. The only required data are readily available: 1)monthly billing data for the energy being used (gas, oil, electricity), and 2) daily temperature data published by the National Oceanic and Atmospheric Administration.; see schematic.