– Analyze and Quantify Water Savings Achieved by Past Programs. In order to analyze and quantify actual water savings achieved due to past program participation, XXX proposes to utilize a “cohort analysis method”, sometimes called a “Differences-to-Differences Method” to measure program- specific water savings at the account-level based on billing history and program participation data for a selected group of water contractors.3 To quantify water savings achieved by a given conservation measure/program, EKI will compare water use before and after implementation of a given intervention for program participants to the water use at geographically- stratified cohort accounts who have not participated in the same or other programs in the given time frame.4 The incremental volume of water saved by program participants compared to that of the cohort can then be attributed to program participation, as all other factors are normalized. Specifically, for residential water users, comparing the change in participating account water use to a non- participating cohort located in the same geographic area (e.g., Census Block Group) effectively controls for factors that can influence water use including, climate, house and yard size, general socio-economic factors, etc. As with the above analyses, programs will be grouped to limit the overall number of analyses to those that are most meaningful for planning purposes (e.g., by fixture or educational outreach type).
