114
ratios for each fuel in Portfolio Manager. Specific calculations and reference documents
each fuel are presented in Section IV.
Table 1
Source-Site Ratios for all Portfolio Manager Fuels
Fuel Type
Source-Site Ratio
Electricity (Grid Purchase)
3.34
Electricity (on-Site Solar or Wind Installation)
1.0
Natural Gas
1.047
Fuel Oil (1,2,4,5,6,Diesel, Kerosene)
1.01
Propane & Liquid Propane
1.01
Steam
1.21
Hot Water
1.28
Chilled Water
1.05
Wood
1.0
Coal/Coke
1.0
Other
1.0
II. The Value of Source Energy
The purpose of the conversion from site energy to source energy is to provide an equit
assessment of building-level energy efficiency. Because billed site energy use include
combination of primary and secondary forms of energy, a comparison using site energy does
provide an equivalent thermodynamic assessment for buildings with different fuel mixes.
contrast, source energy incorporates all transmission, delivery, and production losses, w
accounts for all primary fuel consumption and enables a complete assessment of ene
efficiency in a building.
When source energy is used to evaluate energy performance, an individual buildi
performance does not receive either a credit or a penalty for using any particular fuel type.
contrast, use of a site energy metric would provide a credit for buildings that purchase ene
produced off site by a utility (such as electricity). The following discussion and anal
demonstrate this neutrality. For example, one quarter of the buildings that earned the ENER
STAR in 2006 operate using 100% electricity. This is equivalent to the percent of building
the national population that use 100% electricity. Moreover, the building comparison prese
in Table 3 shows that source energy will correctly recognize efficient heating syst
independent of fuel choice. Therefore, because EPA adopts source energy as the primary un
comparison, using a particular fuel does not in itself make a building more or less likely to
the ENERGY STAR.
Energy Consumption in ENERGY STAR Buildings
Grid Purchased Electricity
When electricity is purchased from a utility, it is a secondary form of energy that is consumed at
a building. Grid electricity is generated through a variety of methods including the burning of
fossil fuels (e.g. coal, natural gas, fuel oil), from nuclear plants, and from renewable sources
including wind, hydropower, and biomass. The source-site ratio for electricity must reflect the
losses that are incurred when these fuels are converted from their primary form into electricity,
and also for any losses that occur on the electric grid as the electricity is transported to specific
buildings.
These values can be computed directly from the Electricity Flow Diagram, included in the
Energy Information Administration’s Annual Energy Review
2
. As shown in the diagram, the
mix of electric production in the United States is approximately 70% fossil fuel, 20% nuclear,
and 10% renewable (hydropower, biomass, solar, wind, geothermal). The source-site ratio is
calculated as Primary Energy (i.e. the total primary energy involved in electricity generation)
divided by Net Generation less Transmission and Distribution (T&D) Losses. This calculation is
summarized in Table 4. As shown, the source-site ratio can be calculated separately for any
given year, and varies slightly over time. Because a building in Portfolio Manager can have
multiple years of data and different buildings have energy data for different time periods, EPA
has computed an average over five years to apply as the standard conversion in the development
of rating models and the rating of individual buildings. The source-site ratio for grid electricity
is 3.340.
Table 4
Source-Site Ratio Calculations for Electricity
Year
Primary Energy Consumed
for Generation
Net
Generation
T&D
Losses
Source-Site
Ratio
2001
38.56
12.69
1.20
3.356
2002
39.56
13.10
1.24
3.336
2003
39.62
13.13
1.24
3.332
2004
40.77
13.49
1.28
3.339
2005
41.60
13.78
1.31
3.336
Average (2001-2005)
3.340
Source:
Electricity Flow (Figure 8.0) in the Annual Energy Review. Values in Quadrillion Btus
(Quads). http://www.eia.doe.gov/emeu/aer/contents.html
On-Site Solar or Wind Electricity
When renewable energy is produced at a building through solar photovoltaic panels or wind
turbines, the goal of the source energy factor is still to account for conversion, transmission, and
distribution loses. In the case of on-site solar or wind energy there is not an analogous
conversion loss because electricity is derived from the sun or the wind, which are not considered
discrete organic fuels, such as fossil fuels. In addition, because the electricity is converted on2
Every year, the Energy Information Administration publishes the Annual Energy Review at:
http://www.eia.doe.gov/emeu/aer/contents.html. This web page also provides links to reports for previous years.
Each report contains and Electric Flow Diagram: http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_3.pdf
Figure 65 - PEF du mix électrique moyen des USA (source : guide méthodologique Energy Star)
Figure 66 - PEF des sources d’énergie locales aux USA (source : guide méthodologique Energy Star)
ratios for each fuel in Portfolio Manager. Specific calculations and reference documents
each fuel are presented in Section IV.
Table 1
Source-Site Ratios for all Portfolio Manager Fuels
Fuel Type
Source-Site Ratio
Electricity (Grid Purchase)
3.34
Electricity (on-Site Solar or Wind Installation)
1.0
Natural Gas
1.047
Fuel Oil (1,2,4,5,6,Diesel, Kerosene)
1.01
Propane & Liquid Propane
1.01
Steam
1.21
Hot Water
1.28
Chilled Water
1.05
Wood
1.0
Coal/Coke
1.0
Other
1.0
II. The Value of Source Energy
The purpose of the conversion from site energy to source energy is to provide an equit
assessment of building-level energy efficiency. Because billed site energy use include
combination of primary and secondary forms of energy, a comparison using site energy does
provide an equivalent thermodynamic assessment for buildings with different fuel mixes.
contrast, source energy incorporates all transmission, delivery, and production losses, w
accounts for all primary fuel consumption and enables a complete assessment of ene
efficiency in a building.
When source energy is used to evaluate energy performance, an individual buildi
performance does not receive either a credit or a penalty for using any particular fuel type.
contrast, use of a site energy metric would provide a credit for buildings that purchase ene
produced off site by a utility (such as electricity). The following discussion and anal
demonstrate this neutrality. For example, one quarter of the buildings that earned the ENER
STAR in 2006 operate using 100% electricity. This is equivalent to the percent of building
the national population that use 100% electricity. Moreover, the building comparison prese
in Table 3 shows that source energy will correctly recognize efficient heating syst
independent of fuel choice. Therefore, because EPA adopts source energy as the primary un
comparison, using a particular fuel does not in itself make a building more or less likely to
the ENERGY STAR.
Energy Consumption in ENERGY STAR Buildings
Grid Purchased Electricity
When electricity is purchased from a utility, it is a secondary form of energy that is consumed at
a building. Grid electricity is generated through a variety of methods including the burning of
fossil fuels (e.g. coal, natural gas, fuel oil), from nuclear plants, and from renewable sources
including wind, hydropower, and biomass. The source-site ratio for electricity must reflect the
losses that are incurred when these fuels are converted from their primary form into electricity,
and also for any losses that occur on the electric grid as the electricity is transported to specific
buildings.
These values can be computed directly from the Electricity Flow Diagram, included in the
Energy Information Administration’s Annual Energy Review
2
. As shown in the diagram, the
mix of electric production in the United States is approximately 70% fossil fuel, 20% nuclear,
and 10% renewable (hydropower, biomass, solar, wind, geothermal). The source-site ratio is
calculated as Primary Energy (i.e. the total primary energy involved in electricity generation)
divided by Net Generation less Transmission and Distribution (T&D) Losses. This calculation is
summarized in Table 4. As shown, the source-site ratio can be calculated separately for any
given year, and varies slightly over time. Because a building in Portfolio Manager can have
multiple years of data and different buildings have energy data for different time periods, EPA
has computed an average over five years to apply as the standard conversion in the development
of rating models and the rating of individual buildings. The source-site ratio for grid electricity
is 3.340.
Table 4
Source-Site Ratio Calculations for Electricity
Year
Primary Energy Consumed
for Generation
Net
Generation
T&D
Losses
Source-Site
Ratio
2001
38.56
12.69
1.20
3.356
2002
39.56
13.10
1.24
3.336
2003
39.62
13.13
1.24
3.332
2004
40.77
13.49
1.28
3.339
2005
41.60
13.78
1.31
3.336
Average (2001-2005)
3.340
Source:
Electricity Flow (Figure 8.0) in the Annual Energy Review. Values in Quadrillion Btus
(Quads). http://www.eia.doe.gov/emeu/aer/contents.html
On-Site Solar or Wind Electricity
When renewable energy is produced at a building through solar photovoltaic panels or wind
turbines, the goal of the source energy factor is still to account for conversion, transmission, and
distribution loses. In the case of on-site solar or wind energy there is not an analogous
conversion loss because electricity is derived from the sun or the wind, which are not considered
discrete organic fuels, such as fossil fuels. In addition, because the electricity is converted on2
Every year, the Energy Information Administration publishes the Annual Energy Review at:
http://www.eia.doe.gov/emeu/aer/contents.html. This web page also provides links to reports for previous years.
Each report contains and Electric Flow Diagram: http://www.eia.doe.gov/emeu/aer/pdf/pages/sec8_3.pdf
Figure 65 - PEF du mix électrique moyen des USA (source : guide méthodologique Energy Star)
Figure 66 - PEF des sources d’énergie locales aux USA (source : guide méthodologique Energy Star)