Energy Intensity Indicators: Residential Buildings Total Energy Consumption

The Figure R1 below reports energy use based on total energy consumption, increases in households, increases in house size, a combined structural component that captures many of the "other explanatory factors," and energy intensity, as index numbers, over the period 1985 to 2004.

  • Activity: Over this period the number of households increased from 86.8 million to 110.7 million (27.5%) while energy consumption increased from 14.7 QBtu to 19.7 QBtu.
  • Energy Use: Residential energy consumption, measured as total energy (i.e., including electricity losses), has increased by about 34% since 1985.
  • Energy Intensity Index: The energy intensity index, based upon energy use per square foot, has generally trended downward since 1985, with the greatest declines observed in the early part of the 1990s.
  • Changes due to factors unrelated to efficiency improvements: As shown in Figure R1, consumption declined in 1990, 1997, 1998 and 2001, years of mild winter weather. The overall effect of non-efficiency related changes has been to increase energy use by about 15.5%
A chart shows five lines representing energy use, number of households, household size, structure including weather, and intensity per square foot for the years 1985 to 2004.  An index with 1985 equal to 1.0 is plotted on the vertical axis; years are plotted on the horizontal axis.  The top line, energy use, is a very wavy line, starting from 1.0 in 1985 and reaching its highest point at 1.34 in 2004.  The second line from the top, number of households, is a smooth line, rising to 1.27 in 2004.  The third line, housing size, is also a smooth line just under the second line, which around 1995 begins to rise at a slower rate than the number of households line, reaching 1.2 in 2004.  The fourth line, structure, dipping slightly under and rising slightly over 1.0 several times during the period, ends slightly under 1.0.  The fifth line, intensity, is slightly undulating, staying near 1.0 through 1990, then drops below 1.0 for the rest of the period, reaching about 0.9 in 2004.

Figure R1. Energy Use, Activity, Intensity and Other Factors in the Residential Sector, 1985-2004

Aside from weather, there are several other explanatory factors that account for energy use that are unrelated to the efficiency of energy use in residences: shifts in the distribution of housing units among regions, and shifts among housing types (from single-family homes to condominiums, for example). The structural index (see structural change under Terminology & Definitions) shown above is a composite of these shifts that also includes the effect of weather, which has a much greater short-term influence on energy consumption than do regional or housing-type shifts. The regional and housing-type shifts together account for the less than a 1% decline in energy consumption over the 1985-2004 time frame.

A vertical bar chart with five sets of three bars shows delivered energy use per U.S. household for the years 1978, 1987, and 1997.  MMBtu/household is plotted on the vertical axis.  The first set of bars on the left shows total household energy use: the left bar, 1978, reaches to about 138; the middle bar, 1987, and the righthand bar, 1997, both reach to 100.  The second set of bars from the left represents heating, showing the 1978 bar reaching about 92, the 1987 bar reaching 55, and 1997 reaching 51.  The three bars in the third set, cooling, are all very short, with 1978 and 1997 both at about 4, and the middle 1987 bar at about 5; the fourth set of bars represents water heating, with 1978 reaching 20, 1987 at about 18, and 1997 at about 18.5.  The last set of bars represents appliances, with 1978 and 1987 equal at 22, and 1997 higher at about 26.

Figure R2. Delivered Energy Use Per U.S. Household by Total and End Use
(Source: 1978, 1987 and 1997 RECS)

Figure R2, above, shows that energy use per household declined substantially over the period 1978-1987, but has changed little, in aggregate since then. While total energy use has remained static between 1987 and 1997, heating and cooling energy use has declined over this period, while appliance energy use increased enough to offset the declines in other end-uses, thus holding total energy use about the same. (These estimates were based upon the Residential Energy Consumption Survey (RECS), a household survey conducted periodically by the Energy Information Administration).