In the run-up to the final rollout of its Clean Power Plan, U.S. EPA has consistently promoted energy efficiency efforts as a cheap, easy and financially advantageous way to meet the rule's ambitious goal of reducing the power sector's greenhouse gas emissions by 30 percent.

"When you look at energy efficiency, it is the best approach to actually address the challenge of carbon pollution in a way that is tremendously cost-effective," EPA Administrator Gina McCarthy said in April at a panel hosted by the University of Chicago's Energy Policy Institute. Efficiency efforts, she said, are "an extreme case of how you can get [to state carbon-reduction goals] at the lowest possible cost."

In fact, EPA has predicted that efficiency improvements undertaken to meet state-level goals will ultimately lower monthly electricity bills for consumers, by lowering overall demand.

But now a paper released by that same institute appears to poke serious holes in EPA's arguments. Examining a major Michigan weatherization program, the study found that while upgrades reduced consumption by about 10 to 20 percent, the total energy savings generated over a 16-year window amounted to less than half of the initial weatherization costs.

These savings were also much lower than initial predictions had estimated. And the study also found that, despite the promise of free weatherization upgrades and long-term savings on energy bills, program administrators had a difficult—and costly—experience convincing Michigan homeowners to participate in the program.