Energy performance ratings tell what the energy performance of a building is, but if the energy performance of a building is to be improved, the causes of lower than desired performance must be understood, and methods of achieving improved performance must be determined. Causes of variation in energy performance among commercial buildings are understood to a degree, but much remains to be learned.
Estimates of potential in energy efficiency improvements of commercial buildings, i.e., the potential to reduce energy use, have, over many years, indicated that a lot has been and still could be accomplished. Issues of economic incentive and resource allocation influence the estimated savings values, but reductions of 20–40%, on average for the entire sector, appear reasonably achievable if a great enough need exists. In the European Union, a potential savings of 40% has been presented as possible. Energy savings of 20% of the worldwide annual commercial sector energy use of 30 quads (35 EJ) is 6 quads/yr (7 EJ/yr), which is about 2% of total world energy use. Unfortunately, energy costs are often not large enough, relative to other costs of running a business or organization, to receive major attention, so efficiency improvements have a lower priority.
Research has indicated many reasons why energy efficiency varies so much in commercial buildings. The causes of variation in energy efficiency change can be categorized as variations in: efficiency of operation, efficiency of systems, and efficiency of equipment. Of these three, about half of the potential improvement for the sector would result from operational improvements, with the remainder from equipment and system improvements.
Many studies have shown the importance of operational improvements, with typical savings of 10–20% possible in a wide range of buildings. Other studies show significant savings from equipment and systems improvements. The United States Federal Energy Management Program is responsible for achieving reductions in annual energy intensity for most U.S. government buildings. Significant reductions have been achieved through attention to all three areas of efficiency improvement: operation, equipment, and systems. From 1975 to 1985, a reduction in annual energy intensity of about 20% was achieved. After 1985, additional goals were required by Executive Order and other means, and the annual energy intensity of U.S. government buildings is on track to reduce annual energy intensity an additional 30% by the year 2005 relative to the year 1985.
The potential for energy efficiency improvements in the commercial sector is large, if the desire to improve is there, as witnessed by the progress in U.S. government buildings. European estimates also show a large savings potential. If the sources of energy inefficiency in commercial buildings can be reduced through attention to the three major areas of efficiency improvement, about a 2% reduction in world energy use appears achievable.
