**Aggregating Site-level Weather Normalized Metered Energy Savings and Quantifying Uncertainty in Aggregate Savings Statistics**

The goal of CalTRACK is to develop replicable, consistent, and methodologically defensible estimators of savings over portfolios of residential single family buildings.

Portfolio-level savings statistics are based on aggregations of site-level savings estimates created using the CalTRACK site-level daily weather normalized metered energy savings analysis methods.

**Recommendations calculating aggregate payable savings for portfolios site-level savings estimates.**

**Total payable savings.** For a portfolio of N projects with valid site-level savings estimates generated using the CalTRACK daily analysis method, the CalTRACK working group recommends portfolio-level total payments based on the unweighted sum of all N site-level estimates (in kWh or therms), whether negative or positive, as below:

Where

is the savings estimate for the ith site in a portfolio.

Because of the potential for abnormally large savings estimates (either positive or negative) caused by unrelated phenomena or statistical noise to skew portfolio total payable savings, the technical working group also recommends a policy for either aggregators or payors to argue for the exclusion of projects from portfolio totals if they are either above a site-level fractional savings of 50% or below a site-level fractional savings of -50%