Energy Intensity Indicators: Delivered Energy
Figure 1 compares intensity indexes using either total energy or delivered energy for the economy as a whole. The indexes diverge in 1989 primarily as a result of a change in the way the Energy Information Administration (EIA) collected data related to the electric utility sector. A new survey, covering information beginning in 1989, resulted in two small changes in how electricity losses are treated.
The first change affects how transmission and other unallocated losses are measured and results in about a 35% increase in such losses in 1989 (this increase was about 2% of total electricity production in 1989) as compared to the immediately preceding years. The index based on delivered energy excludes changes in transmission losses, as those losses are not assigned to any end-use sector.
The second change involves some explicit accounting for the thermal output (e.g. steam) and associated input energy provided to the electric utility sector. In the total energy accounting framework developed by EIA, this small amount of energy for steam is allocated to the individual end-use sectors, and is essentially included with generation and transmission losses. This additional energy use is reflected for the first time in the total energy data by end-use sector for 1989.
These two changes in the energy accounting framework are primarily responsible for the divergence of the two intensity indexes in 1989. After 1990, the temporal changes in the two indexes are almost identical (less than 0.3% difference in the percentage changes between 1990 and 2004). For purposes of measuring the economy-wide intensity change from 1985, the index based on total energy is the preferred measure.
Changes in delivered energy intensity for each of the four end-use sectors and the electricity sector are shown in Figure 2 below. Note that we are showing the electricity producing sector in the figure, because now the end-use sectors are including only the electricity delivered to final users, not including the losses as they were for total energy. In this case, the commercial buildings sector has increased its energy intensity by less than 2% over the period 1985 to 2004 as compared to the 12% increase when total energy is used. The delivered energy intensity in the residential sector has declined by about 18% during that same period. In the transportation sector energy intensity has declined by about 14% from 1985 to 2004. The decline in energy intensity was greatest in the industrial sector, falling by 21% over the 19-year period. Electricity sector intensity has declined nearly 5%.
|Five Sector Energy Intensity Indices for Delivered Energy|
|Transportation||Industrial||Residential Buildings||Commercial Buildings||Electricity|
From the table it is clear that there is no significant difference between transportation energy use whether calculated on a delivered basis of on a total energy basis. Because the transportation sector uses so little electricity, there are virtually no electricity system losses allocated to transportation.