McKinsey and Company’s central conclusion from their U.S. Energy Efficiency report says much about the energy efficiency opportunity in the US:

Energy efficiency offers a vast, low-cost energy resource for the U.S. economy – but only if the nation can craft a comprehensive and innovative approach to unlock it.  Significant and persistent barriers will need to be addresses at multiple levels to stimulate demand for energy efficiency and manage its delivery across more than 100 million buildings and literally billions of devices.  If executed at scale, a holistic approach would yield gross energy savings worth more than $1.2 trillion, well above the $520 billion needed through 2020 for upfront investment in efficiency measures (not including program costs).  Such a program is estimated to reduce end-use energy consumption in 2020 by 9.1 quadrillion BTUs, roughly 23 percent of projected demand, potentially abating up to 1.1 gigatons of green house gases annually.

Unlocking Energy Efficiency in the U.S. Economy – McKinsey and Company