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U.S. Department of Energy Energy Efficiency and Renewable Energy

Energy Intensity Indicators: Residential Buildings Delivered Energy

Figure R1, below, reports residential energy consumption measured as delivered energy, 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: The number of households, the activity measure for this sector, has increased by about 28% since 1985.
  • Energy Use: Residential energy consumption, measured as delivered consumption (i.e., excluding electricity losses), has increased 18% since 1985, compared to a 28% increase in the number of households over the same period. As shown in the graphic below, consumption declined in 1990, 1997, 1998 and 2001, years of mild winter weather.
  • Energy Intensity Index: The residential energy intensity index is based upon a ratio of energy use per square foot of floor area. The intensity index has generally trended downward since 1985, with the greatest declines observed since the early part of the 1990s. By 2004 energy intensity had declined by 18% compared to 1985.
  • Changes due to factors unrelated to efficiency improvements: Since 1993 several structural effects have moderated energy consumption in the residential sector. In 2004 these factors combined to reduce energy use by about 7% as compared to 1985. Long-term shifts in the geographic distribution of households (e.g. north to south) and the types of housing units (e.g. single-family vs. multi-family) were responsible for nearly a 3% reduction in delivered energy in 2004 compared to 1985. Weather factors were responsible for the balance of the change.
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, number of households, is a smooth line, rising to 1.28 in 2004. The second line from the top, housing size, is also a smooth line just under the second line, rises at a slower rate than the number of households, reaching nearly 1.2 in 2004. The third line, energy use, is a very jagged line, starting from 1.0 in 1985 and reaching nearly 1.2 in 2004. The fourth line, structure, dipping slightly under and rising up to or near 1.0 several times during the period, ends slightly over 0.9. The fifth line, intensity, remains near 1.0 through 1989, slowly drops to 0.84 in 1995, slightly rises and drops over the next two years, then gradually drops to near 0.8 in 2004.

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

Figure R2 shows that energy use per household declined substantially over the period 1978-1987, but changed little in the succeeding ten years. While total energy use remained static between 1987 and 1997, heating and cooling energy use 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).

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)