Vast amounts of the energy that is generated for powering society is wasted. The existing model of having large point sources of power generation and transporting the power long distances to demand centers like cities has significant transmission line losses from electrical resistance. Room temperature superconductor technology has not advanced sufficiently to replace the copper wire presently used. Once the power arrives at its destination, there are thermal losses in most devices.
Improving Energy Efficiency of devices that we use in our society is considered one of the cheapest and simplest ways to reduce power consumption reducing the size of the power demand (so called nega-Watts). Enormous amounts of heat are lost in northern climates during the winter, and in southern climates during the summer the air conditioning costs are enormous. In both cases, better insulation in buildings can greatly reduce this loss.
There are numerous sources on the web for getting more information on, here is one from the US Department of Energy, on Energy Efficiency.