Principle] The Jevons Paradox - "It is wholly a confusion of ideas to suppose that the economical use of fuel is equivalent to a diminished consumption. The very contrary is the truth".  The problem with efficiency gains is that we inevitably reinvest them in additional consumption.

Example] Paving roads reduces rolling friction, thereby boosting miles per gallon, but it also makes distant destinations seem closer, thereby enabling people to live in sprawling, energy-gobbling subdivisions far from where they work and shop.

Text] "Brookes argued that devising ways to produce goods with less oil—an obvious response to higher prices—would merely accommodate the new prices, causing energy consumption to be higher than it would have been if no effort to increase efficiency had been made; only later did he discover that Jevons had anticipated him by more than a century. Nowadays, this effect is usually referred to as “rebound”—or, in cases where increased consumption more than cancels out any energy savings, as “backfire."

Link to Full Text] http://www.newyorker.com/reporting/2010/12/20/101220fa_fact_owen#ixzz1A6LS0RZA