National Renewable Energy Laboratory (NREL) & LBNL Technical Report, NREL/TP-6A20-61042 & LBNL-6589E, May 2014.
http://emp.lbl.gov/sites/all/files/lbnl-6589e.pdf

"This report surveys and summarizes existing state-level RPS cost and benefit estimates and examines the various methods used to calculate such estimates. The report relies largely upon data or results reported directly by electric utilities and state regulators."