The amount of energy consumed in the commercial sector often must be estimated as a fraction of energy use in the combined residential and commercial sectors; national energy use in buildings is often tracked within the major sectors, categorized as industrial, transportation, and ‘‘other,’’ with residential and commercial buildings aggregated and accounting for most of the energy use in this ‘‘other’’ sector. Thus some quick checks on world total energy consumption are useful. The units used to sum world energy use are not easily comprehended by most people, so the important knowledge to retain is the relative values. Total world energy consumption in the year 2000 was about 395 quads (1 _ 10 15 Btu), or about 420 EJ (exajoules). Fuel processing, non- energy use of fuels, and other losses reduce the total final energy consumption in the major energy-using sectors to about 270 quads (280 EJ).
Because the importance of energy use in the industrial and building sectors can be misunderstood if losses associated with generation and distribution of electricity are not included, comparisons that show both totals are useful. The estimated sectoral breakouts, without accounting for electricity losses, are 87 quads for industry, 71 quads for transport, and 109 quads for ‘‘other,’’ which is primarily residential and commercial buildings. Adding approximate electricity losses brings the totals to 122 quads for industry, 73 quads for transport, and 156 quads for ‘‘other,’’ for a total of about 350 quads, or 370 EJ.
For the world overall in the year 2000, commercial sector energy use is approximately 30% of the ‘‘other’’ energy use, which amounts to a little over 30 quads (35 EJ) when electricity losses are not included. This energy use represents about 12% of the approximately 270 quads of total final energy consumption for the world. When electricity losses are included, commercial sector energy use is about 45 quads (50 EJ).
Although commercial sector energy use is only 12% of the world total, as economies develop, energy use in this sector tends to rise relative to other sectors and is one of the most difficult to reduce, due to complexities of systems, building ownership, and building uses. The rise in energy use relative to other sectors appears to result from the need for increasingly sophisticated facilities to handle activities in this sector as national economies advance, as well as from a concurrent rise in income within the sector relative to the cost of facilities.
The history of the commercial sector relative to the residential sector in the United States provides an example of this pattern of change. Specialization in services and enterprise management grew significantly in the United States throughout the last half of the 20th century. Allowing some time to pass after World War II, so that wartime effects and rationing-induced behaviors can be discounted, energy use in the commercial sector was about 50% of residential energy use in the year 1960. This ratio grew to about two-thirds by 1980, and in the year 2000 was over 83%. Residential sector energy use in the United States was 20% of total national energy use in both 1960 and 2000, whereas commercial sector use increased from 10 to 17% of the total. Thus, commercial sector energy use was about 30% of sectoral energy use in the building or ‘‘other’’ category in the United States in 1960, but by 2000 had grown to 45% of the building sector total.
Variations among countries and location are dramatic. Although the commercial sector in the United States accounts for about 17% of all energy use, in China it accounts for about 5%. Commercial buildings in rural areas typically are less complicated and use less energy, as compared to those in metropolitan areas; over 80% of commercial sector energy use is in metropolitan areas.
