As important as energy is, and despite our understanding of peak resource curves, and diminishing supplies, we are still very wasteful of energy resources. In the U.S. we waste more than 50% of the energy we consume.
Energy efficiency applies to many areas including homes, commercial buildings, industry, transportation, and electricity generation. With non-renewable energy sources such as coal, oil, natural gas, and nuclear making up the vast majority of the sources of our energy.
Wasting the energy from sources that contribute carbon dioxide and other greenhouse gases (the primary cause of climate change and a key defining characteristic of the anthropocene), can be mitigated through increasing efficiency at various points along the energies life cycle.
(TED x Boulder talk by James Brew - The Value of Energy Efficiency)
However, Jevon's paradox argues that increasing efficiency gains made will only result in more incentive and ability to consume ever greater amounts of that energy - resulting in even more greenhouse gases and climate change.