The Gridium Measurement and Verification model and associated calculations are based upon a Time of Week and Temperature (TOWT) model, originally developed by Lawrence Berkeley National Laboratory (LBNL) and implemented in the open source library “nmecr”. The TOWT model is a whole-building (Option C) baseline regression model that includes terms for:
- the day and hour of the week, and
- piecewise-linear temperature response terms with (configurable) change points creating ranges from 50-60F, 60-70F, 70-80F, etc.
In addition, different regression models are fitted for occupied and unoccupied periods of the day. These periods are determined algorithmically, and the separate models allow for different temperature response curves when the building is open or closed.
We selected this specific technique due to its broad acceptance in the NMEC community and its extensive peer review by academic, utility and regulatory reviewers. It is also a non-proprietary technique which allows us to share the detailed calculations and computer code with utility and regulatory reviewers – an important requirement for utility program incentive programs.
A more detailed yet relatively non-mathematical explanation of the model may be found at the open source project github project site. All calculations follow guidelines for Site-Level NMEC methods issued by the California Public Utility Commission (CPUC), which are built upon ASHRAE Guideline 14-2002.