Demand for heating and cooling has declined over the last 50 years as the U.S. population has migrated to moderate and warmer climates, a university researcher has found. Decreases range from 6% to 12% depending upon the calculation methodology used.
"The relative increases in population in more moderate climates and, at the same time, in warmer climates imply a reduction in the combined energy per person -- the shift to more moderate climates because of narrower ranges between winter and summer temperatures, and the shift to warmer climates because it is more energy-efficient to cool than to heat," said Michael Sivak, a research professor at the University of Michigan Transportation Research Institute.
The study, published in "Cities: The International Journal of Urban Policy and Planning," found that the U.S. population shift has resulted in an 11% reduction in combined energy demand per person for heating and cooling since 1960.
Sivak performed three analyses based on 1960 and 2006 population data for the 50 largest metropolitan areas in the United States, which account for 54% of the U.S. population. The analyses are: nominal energy demand, based only on heating and cooling degree days; effective energy demand, based on heating and cooling degree days incorporating the energy efficiencies of heating and cooling appliances; and practical energy demand, based on degree days and appliance efficiencies, as well as the efficiencies of power generating plants.
Based on climatological considerations only, Sivak found that while the energy demand for cooling (air conditioning) increased by 23% from 1960 to 2006, the demand for heating -- which dominates the combined demand -- decreased by 14%. Overall, the nominal energy demand for both heating and cooling dropped 6%.
Using the effective energy demand approach, which accounts for energy used by furnaces, boilers, electric heaters and air conditioners, Sivak found a 12% reduction in energy demand since 1960.
The most comprehensive practical energy demand measure, which also incorporates the energy used by power plants, yielded an 11% reduction.
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