Lawrence Berkeley National Laboratory, Jan. 2017, by Ian M. Hoffman, Greg Leventis, and Charles A. Goldman.
https://emp.lbl.gov/publications/trends-program-administrator-cost/

"This technical brief presents trends in the cost of saved electricity for energy efficiency programs between 2009 and 2013. We collected and analyzed more than 5,400 program years of data collected in 36 states from 78 administrators of programs funded by customers of investor-owned utilities. These administrators provide efficiency programs to customers of investor-owned utilities that serve about half of total U.S. electricity load."