This article illustrates well the position we now face.
This Blog, however, prefers to speak of the resource intensity of useful energy to fit the concept within the bounding conditions of the ‘One Planet Equation’
Energy efficiency now supposedly lies at the heart of EU and US energy policies. Whilst we are most aware of the merit of energy efficiency of energy consumption, e.g. fuel-efficient cars and well-insulated buildings, the concept of energy efficiency of energy procurementis one that has been largely overlooked. One reason for this has been the vast energy surplus provided by historic supergiant oil and gas fields of the Middle East, Russia and the Americas and vast surface coal deposits of Africa, Asia and Australia. As production from these historic fossil fuel deposits starts to decline, the OECD economies are being forced to procure energy from other sources such as wind, tidal, solar, bio-fuel and nuclear. Without most of us being aware of the fact, it has suddenly become important to understand the energy efficiency of new energy procurement systems, if industrial society as we know it is to survive the next great energy transition away from fossil fuels.
The Energy Return on Energy Invested (ERoEI) provides one measure of the efficiency of energy procurement and is quite simply defined as:
Energy procured / Energy used to procure energy………………..
Complete article http://europe.theoildrum.com/node/5051