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.