Energy Intensity Indicators: Commercial Buildings Delivered Energy
Figure C1, below, reports energy use based on delivered energy consumption, increases in floor space, the weather effect, and energy intensity, as index numbers, over the period 1985 to 2004.
- Activity: Estimated total floor space in commercial buildings grew rapidly during the economic expansion of the 1990's, with 35% more floor space in 2004 as compared to 1985.
- Energy Use: Commercial energy consumption, measured as delivered consumption (i.e., excluding electricity losses), has increased in every year since 1985 with the exceptions of 1990, 1998, 2001, and 2004. By 2004, commercial delivered energy consumption was 36% higher than in 1985.
- Energy Intensity Index: On a delivered energy basis, the overall commercial sector energy intensity in 2004 was about the same as in 1985. The declines observed in 1991 and since 2001 are primarily the result of economic recessions. In these periods, vacancy rates of commercial office and retail space increased and the utilization of occupied space fell.
- Changes due to factors unrelated to efficiency improvements: Energy use in commercial buildings is sensitive to weather, although not to the same degree as in residential buildings. Figure C1 shows the estimated weather factor (as an index), based upon heating and cooling degree-days by census region. The years 1990, 1992, and 1998 stand out; calendar year 1990 contained very warm winter weather and 1992 was an especially cool summer; 1998 was an especially mild winter.
Figure C2 shows energy consumption per square foot of floor space in five building types, for all buildings, and for the residue of other types lumped into an "other" category, for five years when the Commercial Energy Consumption Survey was conducted. In some cases the trend, to the extent there is one, is upward (Education, Health Care and Assembly buildings), in others downward (Offices and Retail/Service buildings).
The sorting out of the effect of other explanatory factors, such as building type, is a work in progress. (These estimates were based upon the Commercial Building Energy Consumption Survey (CBECS), a survey of commercial buildings conducted periodically by the Energy Information Administration). At this stage, however, we are not yet able to quantify these factors in any comprehensive fashion for the system of indicators.