Energy conservation is the effort made to reduce the consumption of energy by using less of an energy service. This can be achieved either by using energy more efficiently (using less energy for a constant service) or by reducing the amount of service used (for example, by driving less). Energy conservation is a part of the concept of eco-sufficiency. Energy conservation reduces the need for energy services and can result in increased environmental quality, national security, personal financial security and higher savings.
It is at the top of the sustainable energy hierarchy.
It also lowers energy costs by preventing future resource depletion.Energy can be conserved by reducing wastage and losses, improving efficiency through technological upgrades and improved operation and maintenance. On a global level energy use can also be reduced by the stabilisation of population growth.
Energy can only be transformed from one form to other, such as heat energy to motive power in cars, or kinetic energy of water flow to electricity in hydroelectric power plants. However machines are required to transform energy from one form to other. The wear and friction of the components of these machine while running cause loss of quadrillions of BTU and $500 billions in industries only in USA. It is possible to minimize these losses by adopting green engineering practices to improve life cycle of the components.(Ref.R.Chattopadhyay:Green Tribology, Green Surface Engineering and Global Warming', ASM International,USA, 2014. Also 3 books by same author published earlier on wear, surface engineering and global warming.)