Energy Efficiency
The discussion above on net energy shows you that it takes energy to get energy and that
some sources of energy require more input than others to get usable energy. After we get
the energy, we then use it for some purpose. Energy efficiency is a term that describes how
much usable energy we have available to do work from every unit of energy that we use.
Higher energy efficiency is desirable because it means we are wasting less energy and getting
more use out of the energy sources that we take from the Earth. Higher energy efficiency
also lets us extend our non-renewable sources and make them last longer.
Nearly 85% of the energy used in the United States comes from non-renewable fossil fuels.
Since these exist in limited supplies, we need to be especially concerned about using them
efficiently. Sometimes our choices affect energy efficiency. For example, transportation needs
require huge amounts of energy. Forms of transportation such as cars and airplanes are less
efficient than transportation by boats and trains. Fluorescent light bulbs are more efficient
than regular, incandescent light bulbs. Hydroelectric power plants are more efficient than
nuclear fission reactors.
Energy Conservation
Energy conservation involves reducing or eliminating the unnecessary use of energy. This
improves energy efficiency. Energy conservation saves us money and it also ensures that our
energy supplies will last longer. There are two main ways to conserve energy: use less energy
and use energy more efficiently. The pie chart (Figure20.10) shows how energy is used in
the United States.
Almost one-half of the energy used in the United States is for transportation and home
use. This means that individual people can do much to conserve energy on a national basis.
Table20.3shows some ways that we can decrease energy use and use energy more efficiently
in transportation, residences, industries, and office settings.