Energy Costs in U.S. Cities. Geography Matters

Energy costs are a significant part of the variable costs of housing. A good share of the energy costs are the result of managing the air temperature: heating in winter and cooling in summer). It is estimated that more than 50 % of the residential energy costs of a typical U.S. household are associated with the costs of either heating or cooling.

Due to the sheer size of the United States the variability of climate conditions is extremely high. Different climatic regions characterize the United States: from continental areas with extremely cold winters in the North to sub-tropical coastal areas in the South-West and South-East.

Thus, the place where a household lives determines the amount of energy needed for climate control to a great extent. In an age of seemingly ever increasing costs for energy information about the difference between specific locations concerning their potential energy costs become increasingly interesting. Information on the potential energy costs may be helpful for households who contemplate about re-locating or have to choose a new residential location.

To determine the potential energy demand two indicators are used which are based on the prevailing climate (temperature) in a given region:

• To determine the energy costs for heating in winter so called “heating degree days” (HDD) are calculated. A heating degree day is a standardized measure to estimate the energy demand to heat buildings. It is calculated by subtracting the average daily temperatures from 18 degree Celsius (which equals 65 degrees Fahrenheit) and then calculating the sum over all positive values for the whole year. For example if a winter day has an average daily temperature of 5 degree Celsius the resulting value for heating degree days is thirteen. The baseline of 18 degree Celsius is chosen to guarantee an in-house temperature of about 21 degree Celsius which is generally assumed to be comfortable to most people.

• To determine the energy costs for cooling in summer so called ”cooling degree days” (CDD) are calculated in an analogous way. The baseline of 18 degree Celsius (65 degree Fahrenheit) is subtracted from the daily average temperatures above this value. For example if a summer day has an average daily temperature of 25 degree Celsius the resulting value of cooling degree days is seven.

Though these variables only use a very rough indicator (temperature) for the given climate, several studies have proven that energy consumption is significantly correlated with these concepts of degree days. Thus, it is not necessary to take other climate variables like humidity, cloud cover or wind patterns into account.

A recent university study analyzed the potential needs for climate control and its geographic variation over the whole continental United States. Specifically, this study undertaken by Michael Sivak (University of Michigan Transportation Research Institute) analyzed the fifty largest metropolitan areas according to their potential energy demand for climate control. These fifty metropolitan areas (cities and their suburbs having at least a population of one million) accounted for about 54 % of the total population of the United States.

The major results of the study by Michael Sivak are as follows:

• In general heating has a much higher weight for determining overall energy demand than cooling. All metropolitan areas with an overall high demand for energy are in areas with cold winters in which the need for heating is high.

• The variation in overall demand for energy is extremely high. The demand for energy in Minneapolis (Minnesota) is more than four times as high as in San Diego (California).

• Demand for cooling outweighs demand for heating is some metropolitan areas but the overall demand for energy is still relatively low there.

• Metropolitan areas with a low overall demand for energy (heating and cooling combined) are clustered in California, Florida and Texas.

• If you prefer relatively cool summers but would like to prevent huge energy bills due to heating you could chose Portland (Oregon) or Seattle (Washington). These metropolitan areas do have low heating due to relatively mild winters and at the same time there is virtually no demand for cooling during summer.

The cited study is published as:

Michael Sivak (2008): Where to live in the United States: Combined energy demand for heating and cooling in the 50 largest metropolitan areas. Cities. The International Journal of Urban Policy and Planning 25, pages 396-398.