The cheapest form of energy is the energy that is not used. Many studies have shown there is a huge potential to improve the energy efficiency of modern society. The high oil prices of the 1970’s encouraged significant improvements in the efficiency of energy use. This trend, however, has not continued in the face of the lower energy prices of the last decade or so.
Barriers to implementing energy efficiency and conservation measures include the low cost of energy over recent times and the apparent low priority given to energy conservation in households, commerce and industry.

Official forecasts of energy consumption include an allowance for projected levels of conservation by consumers , as well as so-called “ demand side management”, where major users reduce their consumption of electricity at times of peak demand.

As with renewable energy, efficiency and conservation have a role to play, but will not remove the need to use fossil fuels and find ways to do so in a less greenhouse gas intensive manner.

One useful approach which places the role of different measures within an overall context, is the “Seven Wedges” model developed by Princeton Professor of Engineering, Robert Socolow, with others.

A short explanation of this model can be found here, and a longer one here.