American Council for an Energy-Efficient Economy (ACEEE), Apr. 2014.
http://www.aceee.org/sites/default/files/publications/researchreports/e1401.pdf

"This study evaluates the implications of using end-use energy efficiency to reduce greenhouse gas emissions from the power sector. It does so by quantifying the energy, economic, and pollution-reduction impacts of selected energy-saving policies on a state-by-state basis. We evaluate four of the most common and effective energy efficiency policy options available to a state:
  • Implement an energy efficiency savings target
  • Enact national model building codes
  • Construct combined heat and power systems
  • Adopt efficiency standards for products/equipment"