Detailed Explanation of Methodology for Commercial Calculations

Commercial Sector Energy Savings
Data on current energy use are from the Energy Information Administration (EIA) 1995 and 1999 Commercial Buildings Energy Consumption Survey (CBECS) data by building type, end use (space conditioning (HVAC), water heating, lighting, cooking, refrigeration, office equipment, and other), and for new construction also by building size and climate (see below). Major energy sources include electricity, natural gas, propane, and fuel oil. RMI calculations based on EIA data were used as the baseline for energy use in new commercial construction.

Energy savings potentials were calculated by RMI and other energy experts by building type and end use as follows:

* For each building category, we assumed, for the purposes of this analysis, that energy efficiency measures would be focused on the areas that used the most energy, and therefore promised the greatest return on investment. The shaded areas are not major energy users for those building types, and therefore energy efficiency efforts in those areas were assumed to not be significant.

* * The Energy Information Administration (EIA) data that drive the Finder's calculations are broken out in a number of different ways: by building type, energy end use (how energy is used in the building), building age, climate, and building size, among others. Data are available for two variables at a time, for example, by building type and energy end use or by building size and climate, but not by three, for example, by building type, climate, and energy end use. Although the most accurate results could be obtained by including as many of these variables as possible, these data limitations (and the scope of the data entry section, which was designed to be an "overview" exercise, not an exhaustive building-by-building audit) required the designers of the Finder to use just two variables.

For existing commercial space, the Finder uses building type (e.g. office and lodging) and energy end use (e.g. heating and lighting), which the designers felt best supported both data collection and targeting of energy efficiency programs. (It's more reasonable to target a particular sector--e.g. the lodging industry than it is to implement energy efficiency in all buildings older than 25 years in age.) In summary, for commercial building calculations, the Finder uses a national average of energy consumption for a particular type of building by energy end use .

For new commercial space, the Finder distinguishes first between buildings that are smaller than 50, 000 square feet and those that are larger than 50, 000 square feet. For those that are smaller than 50, 000 square feet, energy savings estimates are then calculated by climate zone and energy end use . For buildings that are larger than 50, 000 square feet, savings estimates are calculated by energy end use only.

The reasoning for this is as follows: Buildings that are smaller than 50, 000 square feet have energy demands that are " skin dominated." That is, heating and cooling energy demands are largely driven by climate and are heavily influenced by how well-suited the building skin, or envelope, is for that climate. Buildings that are larger than 50, 000 square feet typically have energy demands that are " load dominated." That is, heating and cooling energy demands are largely driven by the internal loads of the building (predominantly the heat produced by lighting, equipment and people), which are large enough to dwarf climate-related energy demands.

CBECS data on fuel types used for space heating, cooling, water heating, and cooking were used to calculate energy savings, dollar savings, and emissions reductions. (Ventilation, lighting, and refrigeration were assumed to be 100 percent electric.) For example, natural gas is used to heat water for 51 percent of the commercial floorspace, electricity 43 percent, fuel oil 4 percent and propane 2 percent.

Example of how total energy savings estimates are calculated for the results section:

Energy Savings
Energy savings for water heating is estimated to be 20 percent on the low end for existing buildings used for educational purposes. That 20 percent savings estimate is applied individually to each of the different energy sources used for water heating. This is important, because each fuel source has different costs and emissions factors, with electricity being the highest in both categories, and to obtain accurate results, each source must be treated individually. The estimates of savings potential in water heating is then calculated as a weighted average based on all energy sources used for water heating. The same is done for all other energy end uses. Then the total energy savings potential for the low estimate is calculated as a weighted average based on the percent of total energy use dedicated to each of the major energy end uses. The same process is repeated for each building type for the low and the high estimate. For new construction, building types are first separated by size (greater than or less than 50, 000 square feet) and the calculations are performed in a similar manner, but with climate (instead of buildling type) as an additional distinguishing factor for buildings smaller than 50, 000 square feet.

Dollar Savings
The Finder relies on your data (or default data) for the costs of electricity, natural gas, fuel oil, and propane to calculate current energy expenditures and cost savings. As with the energy savings, dollar savings were calculated by applying savings factors to the costs of each fuel type used in each energy end use (such as space conditioning and water heating).

Emissions Reductions
The Finder generates data on fossil fuel emissions (and reductions in emissions) for three major pollutants: carbon dioxide (CO2), sulfur oxides (SOx), and nitrogen dioxide (NO2). Additional toxic air pollutants such as mercury, which can be released from a number of sources including coal fired power plants and waste incinerators, are of great concern, but are not included in this analysis due to a lack of reliable, accessible data. Calculations on emissions and emissions reductions for natural gas, fuel oil, and propane are derived from standard emissions factors from the Energy Information Administration.

Data on emissions associated with electricity are from one of twenty-seven power regions in the U.S. power grid. Users can access these data from the EPA’s Power Profiler tool, which is populated by data from the eGRID database, a comprehensive source of data on the environmental characteristics of virtually all electric power generated in the United States. The twenty-seven power regions are the finest level of detail for which accurate data are available.

Emissions reductions for electricity are assumed to be reductions in source energy, or the energy produced at the power source, as opposed to site energy, or delivered energy, which is diminished by line losses—the loss of electricity during transmission from the power source to the consumer. Therefore, by basing emissions reductions on source electricity reductions, we are assuming that each kilowatt-hour saved by a consumer equals a kilowatt-hour saved at the power source

Job Creation
Estimates of jobs created from energy efficiency programs are derived from a model developed by John “Skip” Laitner at the U.S. EPA. Skip can be reached at Laitner.Skip@epamail.epa.gov for questions.