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Cal-Arch: A California Building Energy Tool for Owners and Operators

Researchers in EETD's Commercial Buildings Systems Group have developed an interactive, web-based diagnostic tool that enables California building owners and operators to compare energy use in similar buildings. Their work is part of a three-year program to analyze energy use in California's commercial buildings.

Commercial buildings account for about one-third of all electricity consumption in California and consume about $18 billion in energy costs. Efforts during the past 20 years have brought about significant increases in building energyefficiency, but the savings are still well below technical and economic potential.

Cal-Arch, the web-based diagnostic tool, was developed by EETD's Mary Ann Piette, Saki Kinney, and Brian Smith. Based on another EETD benchmarking tool called Arch, this localized version uses a data set compiled from California commercial building energy use data. The data set, the Commercial End- Use Survey (CEUS), was developed from 2,500 commercial on-site surveys, monthly energy use bills, and load research data from California utilities Pacific Gas & Electric and Southern California Edison. The CEUS data provide annual energy-use estimates and hourly load profiles for the commercial sector.

Cal-Arch (http://poet.lbl.gov/cal-arch/) makes it possible for building owners and operators to see how their buildings, stack up against other buildings of the same type. After entering data in a few fields on a web page—building activity, floor area, energy consumption, and ZIP code—and clicking a "comparison" button (see Figure), the user receives a graphic representation comparing the building's energy use with that of similar buildings. The histogram is interpreted for the user on subsequent web pages. Additional information includes a summary table, which shows data for the corresponding energy-use intensity. The data can be viewed in both site or source energy units.

The x-axis shows the values of the histograms bins, which, in the figure above, have a width of 25 kbtu/sqft-yr. The left-hand y-axis corresponds to the vertical bars and is displayed as percent frequency, that is, the percent of all buildings displayed

Figure. The x-axis shows the values of the histograms bins, which, in the figure above, have a width of 25 kbtu/sqft-yr. The left-hand y-axis corresponds to the vertical bars and is displayed as percent frequency, that is, the percent of all buildings displayed in a given bin. The righthand y-axis corresponds to the black lines and gives the cumulative percent frequency, that is, the percent of all buildings to the left of a given point.

In the figure above, the percent frequency corresponding to Your Building is about 22%. In other words, approximately 22% of buildings in the comparison data set use between 25 and 50 kBtu/sqft-yr. The corresponding cumulative percent frequency is about 30%, i.e., 30% of the comparison buildings use less than 50 kBtu/sqft-yr. Although the building is not inefficient, the histogram suggests that there is room for energy-efficiency improvements to make a difference. See the Cal-Arch web site for more information.

"Cal-Arch provides an easy-to-use tool that allows building owners and operators to quickly compare how their building's energy use compares with others. We have found it to be of great interest to this audience," says Mary Ann Piette.

Site results need to be interpreted with caution. Low energy use does not mean that a building is efficient, nor does high energy use mean it's inefficient. Factors such as structure, level of service, and occupancy affect energy use. However, even buildings considered efficient can have significant energysavings potential. A tool such as Cal-Arch can be a valuable resource for building owners and operators looking for methods to cut back on energy use and save money.

— Ted Gartner

For more information, contact:

  • Mary Ann Piette
  • (510) 486-6286; fax (510) 486-4089

For more information, see the Cal-Arch web site.

This work is funded by the California Energy Commission's Public Interest Energy Research (PIER) Program, and the Department of Energy.

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