The California Public Utilities Commission (CPUC) recently funded a study in which local area aggregated electricity and natural gas consumption in California from 2006 through 2010 were analyzed econometrically. Data were available to estimate electricity energy efficiency program impacts for two of the three large California investor-owned utilities. The findings indicate that net savings from these programs for the 2006-2010 period amounted to 11,391 GWh, or 7.3 percent of annual electricity consumption. This point estimate is 50 percent higher than the CPUC approved deemed savings, or ex ante, aggregated gross impact estimate. The econometric approach also enabled quantification of the accuracy of net savings estimates - the relative error of the net reduction in total electricity consumption was 30 percent (at the 90 percent confidence level). The project included an initial assessment of how the results of the aggregate econometric approach could be applied to retrospective empirical estimation of the contribution of energy efficiency programs to meeting California’s greenhouse gas emissions reduction goals under AB32.