Building Integration Tutorial

Commercial Buildings: Office Buildings

According to the Commercial Building Energy Consumption Survey (EIA, 1995), the average office building is 14,900 square feet and office buildings represent 18 percent of the total commercial floor space in the US. Typical subcategories under the classification of office building include:

• Banks or other Financial Institutions
• Doctors’ or Dentists’ Offices
• Government Offices
• Administrative or Professional Offices
• Research and Development Buildings

Although office buildings represent the second largest amount of buildings and floor space, they consume the most energy of all building types, accounting for 19 percent of all commercial energy consumption.  They use a total of 1.0 quadrillion Btu of combined site electricity, natural gas, fuel oil, and district steam or hot water.  The relative consumption of these different energy sources are:

• Electricity: 66%
• Natural Gas: 23%
• District Heat: 7%
• Fuel Oil: 3%

The average end use of these energy sources in U.S. office buildings can be classified as follows:

The cost intensity for typical small and large office buildings in California is in the range $2.5-3/square foot-year when no DG is integrated.
In addition, the approximate electric load of office buildings in the U.S. is as follows:

The US average electricity demand to thermal demand ratio (E/T) for an office building is 2.30. However, if only domestic hot water thermal load is considered (removing the seasonal space heating load, which is not always met by centralized hot water or steam), the E/T achieves 8.72. Available DG-CHP technologies have electric to thermal ratios in the range of 0.5 to 2.5. Therefore, office buildings can only be target applications when space heating needs are incorporated and/or when traditional electric cooling systems are replaced by advanced absorption cooling systems that can be thermally activated by the DG waste heat. The estimated DG-CHP technical potential (no economics considered) for all the office building applications in the US is about 18,000 MW and the market potential (based on achievable economics) is 10,000 MW. In California alone, this technical potential is as high as 2,360 MW.

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