Fred J. Sissine Efficiency and Conservation Defined Energy efficiency is increased when an energy conversion device, such as a steam turbine, undergoes a technical change that enables it to produce more heat or electricity from the same amount of fuel. Energy efficiency is also improved when an energy end-use device, such as a household appliance or commercial building, undergoes a technical change that allows it to provide the same service while using less energy.
Energy is conserved when efficiency is improved or when energy waste is avoided.
The latter occurs, for example, when a computerized thermostat saves on furnace energy use by lowering the household temperature in winter when the house is unoccupied. Another example is the use of heat left over from an industrial process to raise steam for producing electricity. That is, energy curtailment occurs when saving energy causes a reduction in services or sacrifice of comfort. Energy efficiency savings occur as the Nation's stock of appliances, automobiles, industrial equipment, and buildings are either replaced by more energy-efficient stock or are otherwise modified to reduce energy waste. The new stock or modifications come into use through the operation of market forces or through governmental and utility programs.