McKinsey Global Institute (MGI) reports that an additional annual investment in energy productivity of $170 billion through 2020 could cut global energy demand growth by at least half—the equivalent of 64 million barrels of oil a day or almost one and a half times today’s entire U.S. energy consumption.
MGI research suggests that the economics of investing in energy productivity—the level of output we achieve from the energy we consume—are very attractive. With an average internal rate of return of 17 percent, such investments would generate energy savings ramping up to $900 billion annually by 2020. . . .
Moreover, the opportunities to boost energy productivity use existing technologies that pay for themselves and therefore free up resources for investment or consumption elsewhere.
MGI has put a figure on how much it would cost and how much "energy productivity" could reduce our energy consumption and corresponding green house gas (GHG) emissions which, by there reasoning, is affordable. Because none of this investment is in renewables the effect of these technologies on GHG emissions is in addition to the energy savings.
Thanks for tip from Richard Stubi of Cleantech Blog