In this month's Atlantic, Lisa Margonelli writes:

The U.S. economy wastes 55 percent of the energy it consumes, and while American companies have ruthlessly wrung out other forms of inefficiency, that figure hasn’t changed much in recent decades. The amount lost by electric utilities alone could power all of Japan.

A 2005 report by the Lawrence Berkeley National Laboratory found that U.S. industry could profitably recycle enough waste energy—including steam, furnace gases, heat, and pressure—to reduce the country’s fossil-fuel use (and greenhouse-gas emissions) by nearly a fifth. A 2007 study by the Mc­Kinsey Global Institute sounded largely the same note; it concluded that domestic industry could use 19 percent less energy than it does today—and make more money as a result.

Economists like to say that rational markets don’t “leave $100 bills on the ground,” but according to McKinsey’s figures, more than $50 billion floats into the air each year, unclaimed by American businesses. What’s more, the technologies required to save that money are, for the most part, not new or unproven or even particularly expensive.

When I hear about $100 bills left on the ground, I think "regulation." Bingo:

The Clean Air Act has succeeded spectacularly in reducing some forms of air pollution, but perversely, it has chilled efforts to reuse energy: because many of these efforts involve tinkering with industrial exhaust systems, they can trigger a federal or local review of the plant, opening a can of worms some plant managers would rather keep closed.

Much more problematic are the regu­lations surrounding utilities. Several waves of deregulation have resulted in a hodgepodge of rules without providing full competition among power generators. ... [M]any industrial plants cannot themselves use all the electricity they could produce: they can’t profit from aggressive energy recycling unless they can sell the electricity to other consumers. Yet by­zan­tine regulations make that difficult, stifling many independent energy recyclers.