Performance period outputs are generated by calculating a counterfactual in the performance period and comparing it to actual energy consumption values. One model is fit to the baseline (pre-intervention) period consumption. A counterfactual is calculated by applying reporting (post-intervention) period weather data to the baseline model. This is the default method defined in CalTRACK for pay-for-performance programs.
In the context of pay-for-performance efficiency programs, savings calculated using this method (also referred to as metered payable savings) represent the total measured energy reduction associated with an energy efficiency project or set of projects that actually materialize during the performance period. That’s why it’s used as the performance metric in pay-for-performance settings and non-wires alternatives procurements. In these applications, the actual impact on the grid is what matters, rather than an idealized estimate. The following derived quantities are typically generated from performance period analyses:
Counterfactual: The counterfactual is calculated by first analyzing the relationship between energy consumption and outdoor temperature in the baseline period. The performance period weather is substituted into the baseline model to determine what consumption would have been if the intervention had never happened.
Avoided Energy Use: Avoided energy use is calculated as the difference between the counterfactual and the actual energy consumption during the reporting period.
Savings Uncertainty: Since savings are calculated as the difference between a model output and a metered values (theoretically these have no uncertainty), the overall savings uncertainty is simply equal to baseline model uncertainty.