Primary energy includes power derived from steam, oil,
natural gas, and coal in addition to electricity. The difference in
lighting energy consumption in homes and in commercial buildings is significant.
The planning process for constructing commercial buildings now generally
includes detailed lighting designs. In the past, such planning often lumped the
lighting design in with the overall electrical installation or handled by the
architect, if there was a lighting design at all.
Today, trained professionals
evaluate not only the optimum levels of illumination in various spaces, but also
how lighting will affect the energy consumption of a building. Many local
governments are adopting building codes that place an upper limit on the amount
of energy a new commercial building can use per unit area of floor space.
To read the chart above, a definition is
needed. A common measurement of energy is the
British Thermal Unit or BTU. A BTU is the quantity of heat needed to raise the
temperature of one pound of water one degree Fahrenheit. "Quad" in the
chart stands for one quadrillion BTUs, and is a measure often used in energy
Chart by Lee R. Anderson, compiled from information in "DOE
Core Databook," 7
June 1996, U.S. Department of Energy.