Driving and the Built Environment The Effects of Compact Development on Motorized Travel, Energy Use, and CO2 Emissions -- Special Report 298 (2009) / Chapter Skim
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5 Potential Effects of More Compact Development Patterns on Vehicle Miles Traveled, Energy Use, and CO2 Emissions
5 Potential Effects of More Compact Development Patterns on Vehicle Miles Traveled, Energy Use, and CO2 Emissions
Pages 144-199
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From page 144... ...
In addition, more compact development is likely to reduce energy use and CO2 emissions by improving the energy efficiency of buildings, a topic that is also briefly considered. The third section provides a more general discussion of other benefits and costs of more compact, mixed-use development patterns; no attempt is made to quantify these benefits and costs, which was beyond the scope of this study.
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From page 145... ...
If estimates of reductions in VMT are to be translated into savings in energy use and CO2 emissions, one must make a further set of assumptions about the fuels and fuel economy of future vehicles. Will cars continue to be powered by internal combustion engines or hybrids running on fossil fuels, or will all-electric, hydrogen, or other more novel forms of propulsion emerge to play a significant role?
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From page 146... ...
Separate models are developed for personally owned vehicles and transit. The models are calibrated by using individual data from the 1995 Nationwide Personal Transportation Survey, but the variables describing the built environment of households are limited, and there is no control for self-selection.
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From page 147... ...
Comparing the estimates of the above two studies would require limiting the Ewing et al. estimates to the VMT reduction resulting from compact development and ignoring the CO2 reduction factors described above.
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From page 148... ...
The base case assumes that current land use and travel patterns, which are heavily weighted toward suburban development and automobile-dependent travel, will continue into the future, producing a further decline in the overall average density of metropolitan areas, while the two alternative scenarios assume more compact, mixed-use development patterns. Two forecasting periods are analyzed: the first to 2030 and the second to 2050.
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From page 149... ...
in the paper commissioned for this study and is reported as a range, with a broader spread in 2050 than 2030 because of the greater uncertainties.4 The base case assumes that all new (and replacement) housing will be built at the average density of new development during the 1990s, which was about 30 percent below average density levels at the end of the decade.5 The two alternative scenarios channel some fraction of the new growth from new household formation and from replacement of existing housing units into more compact development.6 Scenario 1, 4 The growth in new households closely follows Nelson's projections to 2030 (Nelson 2004; Nelson 2006)
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From page 150... ...
Scenario 1 assumes a 12 percent reduction in household VMT for new housing built at double the average density of existing housing. Scenario 2 assumes a 25 percent reduction, which brackets the reductions at a regional scale found in the literature (see Table 3-1 in Chapter 3)
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From page 151... ...
The committee uses the reference case from that NRC study.11 This scenario assumes improvements in gasoline internal combustion engine technology to meet the new cor porate average fuel economy (CAFE) standards by 2020, expected in compliance with the Energy Independence and Security Act of 2007.12 After 2020, fuel economy continues to 10 More specifically, Scenario 1 assumes that the annual household VMT of new housing built at lower densities would be 8.4 percent higher (12 percent 0.70)
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From page 152... ...
The sensitivity of the results is tested in a later section using a more aggressive fuel economy scenario. Estimates of CO2 emissions are derived from the fuel use projections on the basis of Environmental Protection Agency (EPA 2005)
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From page 153... ...
The decline in fuel use after 2010 reflects the introduction of fuel economy improvements to meet the more stringent CAFE standards.
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From page 154... ...
Percent of new and 0% 25% 75% replacement units compact New and replacement 2030 0.0–0.0 11.5–14.2 34.4–42.5 units compact (in millions) Changes in VMT Assumptions Percent change in 0% 0% 0% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2030 21,187 21,187 21,187 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2030 new noncompact development −12% −25% Percent reduction in VMT/household in new compact development 20,211b 18,671b VMT/household in 2030 new compact development
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From page 155... ...
Changes in Energy Use and CO2 Emissions Assumptions Percent change in 58.5% 58.5% 58.5% fleet mpg by 2030 Fleet mpg 2000 19.5 19.5 19.5 2030 30.9 30.9 30.9 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2030 Results −12.0% to −5.2% −12.9% to −6.3% Percent change in fuel use between 2000 and 2030 Fuel use (in billions 2000 114.3 114.3 2030 (1) c of gallons)
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From page 156... ...
2000 1,006 1,006 2030 (2) d 910–984 849–909 −1.0% to −1.2% −6.7% to −7.7% Percent change in CO2 emissions from base case −8.9 to −11 −61 to −75 CO2 emissions 2030 (millions of metric tons)
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From page 157... ...
Percent of new and 0% 25% 75% replacement units compact New and replacement 2050 0.0–0.0 15.6–25.8 46.8–78.4 units compact (in millions) Changes in VMT Assumptions Percent change in 0% 0% 0% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2050 21,187 21,187 21,187 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2050 new noncompact development −12% −25% Percent reduction in VMT/household in new compact development 20,211b 18,671b VMT/household in 2050 new compact development (continued on next page)
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From page 158... ...
Changes in Energy Use and CO2 Emissions Assumptions Percent change in 68.7% 68.7% 68.7% fleet mpg by 2050 Fleet mpg 2000 19.5 19.5 19.5 2050 32.9 32.9 32.9 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2050 Results −11.0% to +13.2% −12.1% to +11.2% Percent change in fuel use between 2000 and 2050 Fuel use (in billions 2000 114.3 114.3 2050 (1) c of gallons)
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From page 159... ...
Note that the scenarios project some reductions in energy use and CO2 emissions even in the base case, in which the density of new development is lower than current densities. These reductions occur because the base case assumes that the fuel economy of motor vehicles increases and the growth in VMT per household in existing developments stabilizes with the aging of the baby boomers and the continuing decline in household size.
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From page 160... ...
10,000,000 9,000,000 Baseline Low HH 8,000,000 Scenario 2 Low HH 7,000,000 Baseline High HH VMT (in millions) Scenario 2 High HH 6,000,000 5,000,000 4,000,000 3,000,000 2,000,000 1,000,000 0 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 Year (b)
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From page 161... ...
160,000 140,000 120,000 Gallons (in millions) 100,000 80,000 60,000 Baseline Low HH Scenario 2 Low HH 40,000 Baseline High HH Scenario 2 High HH 20,000 0 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 Year (b)
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From page 162... ...
1,400 1,200 (in millions of metric tons) 1,000 CO2 Emissions 800 600 Baseline Low HH 400 Scenario 2 Low HH Baseline High HH 200 Scenario 2 High HH 0 2000 2005 2010 2015 2020 2025 2030 2035 2040 2045 2050 Year (b)
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From page 163... ...
Changing Fuel Economy Assumptions Table 5-3 summarizes the results if a more aggressive fuel economy scenario is assumed. This more aggressive scenario is drawn from the NRC study (2008)
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From page 164... ...
Committee's Original Scenarios Assumptions VMT per household 0 0 Fleet mpg 59 69 Results: fuel use and CO2 emissions Scenario 1 −5 to −12 −11 to +13 Base case in 2000 −6 to −13 −12 to +11 25 percent compact development Scenario 2 −2 to −9 −8 to +19 Base case in 2000 −10 to −15 −15 to +5 75 percent compact development More Aggressive Fuel Economy Scenario Assumptions Fleet mpg 104 194 Results: fuel use and CO2 emissions Scenario 1 −26 to −31 −35 to −49 Base case in 2000 −27 to −32 −36 to −49 25 percent compact development Scenario 2 −24 to −30 −32 to −47 Base case in 2000 −30 to −34 −39 to −51 75 percent compact development Higher VMT Growth Scenario Assumptions +7.8 +13.3 VMT per household Results: VMT Scenario 1 +39 to +62 +70 to +116 Base case in 2000 +38 to +60 +68 to +112 25 percent compact development Scenario 2 +54 to +67 +76 to +127 Base case in 2000 +44 to +54 +61 to +102 75 percent compact development Results: fuel use and CO2 emissions Scenario 1 −12 to +2 +1 to +28 Base case in 2000 −13 to +1 −0.4 to +26 25 percent compact development Scenario 2 −2 to +5 +4 to +34 Base case in 2000 −3 to −9 −4 to +19 75 percent compact development Note: See Annex 5-1 Tables 1 through 4 for details.
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From page 165... ...
, the impacts of continuing improvements in fuel economy beyond 2020 on energy use and CO2 emissions significantly outstrip those from more compact development. 17 The more aggressive fuel economy scenario assumes mpg improvements similar to those of the reference case used in the committee's scenarios up to 2020.
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From page 166... ...
. The effects on energy use and CO2 emissions are more modest because the improvements in fuel economy, even under the less aggressive reference scenario, more than offset the increases in VMT per household.
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From page 167... ...
Second, if the introduction of new technologies is successful -- resulting in a vehicle fleet that is much more fuel-efficient than today's fleet and has a much larger mix of alternatively fueled vehicles -- these changes will lower the baseline energy use and CO2 emissions levels from which reductions from more compact development are calculated. The sensitivity analysis mentioned previously, which assumes a more aggressive fuel economy scenario, illustrates this point.
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From page 168... ...
To the extent that energy use and CO2 emissions are more of an issue than VMT, plausible improvements in vehicle fuel economy will generate significantly larger and more rapid improvements than increases in compact, mixed-use development. Relaxing the scenario restriction on infilling new housing within existing developments, thereby increasing density, would increase projected benefits from compact development.
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From page 169... ...
, and existing development is assumed to have the average density levels of the housing 20 As discussed in more detail in Appendix C, the NRI data measure DUs per acre of developed urban land. The census data measure DUs per gross acre, including land used for nonresidential purposes, but enabling land area to be classified by a range of densities.
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From page 170... ...
The new average density levels for each scenario were then compared with the baseline scenario in 2030 and 2050. Only the results for 2050 are discussed below, since this time frame allows sufficient time for projected changes in development patterns to take hold.
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From page 171... ...
Other members believed that the substantial infill or curbing of large-lot development at the urban fringe, or both, implied in achievement of the targets in Scenario 2 would require such a significant departure from current housing trends, land use policies of jurisdictions on the urban fringe, and public preferences
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From page 172... ...
As a consequence, Atlanta's built environment dropped from an already low density of 1.30 housing units per urbanized acre to 1.08, while Phoenix's comparatively high density of 2.37 grew to 2.73. Results from the 1990 and 2000 U.S.
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From page 173... ...
The most important public decisions have to do with land use planning, public land ownership, and infrastructure. • Phoenix has aggressively pursued land purchases and land banking over the past several decades, using proceeds from a voterapproved dedicated sales tax to create a land trust that collars much of the northern and southern desert reaches of Phoenix.
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From page 174... ...
174 Driving and the Built Environment Box 5-1 (continued) phoenix and atlanta A Comparison of Density Changes in Two Rapidly Growing Metropolitan Areas development of higher-density housing; permitted single family lot sizes are also typically smaller than in metropolitan Atlanta.
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From page 175... ...
Calculations conducted for this study revealed that moving from a 2,400-ft2 single-family home -- the average home size in the United States in 200723 -- to a 2,000-ft2 apartment would save about 34.1 million Btu and about 3.3 metric tons of CO2 emissions, all else being equal (see Annex 5-1 Table 5 for detailed calculations) .24 By 22 Of the four end-use sectors -- transportation, industrial, commercial, and residential -- the residential sector accounted for 20.7 percent of consumer expenditures for energy and 20.4 percent of CO2 emissions (EIA 2007, Tables 3.6 and 12.3)
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From page 176... ...
These energy savings translate to a reduction of 12 million to 14.8 million metric tons of CO2 emissions and 115.1 million to 25 The average multifamily dwelling unit is 1,078 ft2.
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From page 177... ...
d Assumes moving from a 2,400-ft2 single-family dwelling unit to a 2,000-ft2 single-family dwelling unit. 142.2 million metric tons of CO2 emissions, respectively.26 By 2050, the energy savings from downsizing to smaller single-family DUs or moving to multifamily DUs grow to 191.6 trillion to 320.9 trillion Btu and 1,596 trillion to 2.673 trillion Btu, respectively, and savings in 26 The energy savings in 2030 represent a 4 percent to a 37 percent reduction from downsizing to a smaller single-family DU and moving to a multifamily DU, respectively, from a base case that assumes no downsizing.
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From page 178... ...
have enumerated many of the other benefits and costs of more compact, mixed-use development, or conversely, the costs (and benefits) of more sprawling development patterns.
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From page 179... ...
Nevertheless, in the longer run, more compactly developed environments that reduce automobile dependence should leave residents with more travel options as they face potentially higher energy costs and possible carbon taxes. The potential benefits of more compact development in reducing congestion and pollution are more ambiguous.
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From page 180... ...
. Human health effects of increased daytime surface temperatures, reduced nighttime cooling, and higher air pollution levels associated with urban heat islands include respiratory difficulties, heatstroke, and heat-related mortality (EPA 2008)
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From page 181... ...
As noted in Chapter 4, moreover, it is unclear that more compact development would greatly restrict housing choices or increase single-family housing prices because exclusionary zoning may have forced a greater mix of single-family housing units than consumers wanted in the past. Moreover, building more compact, mixed-use developments does not necessarily mean building only multifamily housing.
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From page 182... ...
If the residents of compact developments drive only 5 percent less -- the lower bound of available estimates -- then the savings in energy use and CO2 emissions are less than 1 percent below the base case even by 2050. Thus, the committee believes that reductions in VMT, energy use, and CO2 emissions resulting from compact, mixed-use development would be in the range of less than 1 percent to 11 percent by 2050, although the committee members disagreed about whether the changes in development patterns and public policies necessary to achieve the high end of these findings are plausible.
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From page 183... ...
Similarly, if the energy efficiency of residential heating and cooling is improved, the advantages of shifting from detached single-family homes to apartments or to smaller single-family units will also decline. Indeed, a sensitivity analysis of the committee's assumptions about fuel economy shows that more aggressive fuel economy improvements would produce savings in energy use and CO2 emissions many times the size of those from compact development.
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From page 184... ...
Moreover, housing preferences may change in the future with changes in the demographic and socioeconomic characteristics of the population. references Abbreviations EIA Energy Information Administration EPA Environmental Protection Agency NAHB National Association of Home Builders NRC National Research Council TRB Transportation Research Board
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From page 185... ...
2001. Travel and the Built Environment: A Synthesis.
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From page 186... ...
2005. Special Report 282: Does the Built Environment Influence Physical Activity?
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From page 187... ...
Percent of new and 0% 25% 75% replacement units compact New and replacement 2030 0.0–0.0 11.5–14.2 34.4–42.5 units compact (in millions) Changes in VMT Assumptions Percent change in 0% 0% 0% VMT/household in existing development VMT/household in 2000 21,187 21,187 21,187 existing 2030 21,187 21,187 21,187 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2030 new noncompact development (continued on next page)
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From page 188... ...
Changes in Energy Use and CO2 Emissions Assumptions Percent change in 103.6% 103.6% 103.6% fleet mpg by 2030 Fleet mpg 2000 19.5 19.5 19.5 39.7c 39.7c 39.7c 2030 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2030 Results −31.5% to −26.2% −32.2% to −27.1% Percent change in fuel use between 2000 and 2030
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From page 189... ...
2000 1,006 1,006 2030 (2) d 708–766 661–707 −1.0% to −1.2% −6.7% to −7.7% Percent change in CO2 emissions from base case −7 to −9 −47 to −59 Change in CO2 2030 emissions from base case (millions of metric tons)
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From page 190... ...
Percent of new and 0% 25% 75% replacement units compact New and replacement 2050 0.0–0.0 15.6–25.8 46.8–78.4 units compact (in millions) Changes in VMT Assumptions Percent change in 0% 0% 0% VMT/household in existing development VMT/household in 2000 21,187 21,187 21,187 existing development 2050 21,187 21,187 21,187 Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2050 new noncompact development −12% −25% Percent reduction in VMT/household in new compact development
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From page 191... ...
Changes in Energy Use and CO2 Emissions Assumptions Percent change in fleet 193.8% 193.8% 193.8% mpg by 2050 Fleet mpg 2000 19.5 19.5 19.5 57.3e 57.3e 57.3e 2050 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2050 Results −48.9% to −35% −49.5% to −36.1% Percent change in fuel use between 2000 and 2050 Fuel use (in billions 2000 114.3 114.3 2050 (1) c of gallons)
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From page 192... ...
d The baseline projections for 2050 reflect the assumptions described in Footnote b. e Assumes more aggressive fuel economy improvements.
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From page 193... ...
Percent of new and 0% 25% 75% replacement units compact New and replacement 2030 0.0–0.0 11.5–14.2 34.4–42.5 units compact (in millions) Changes in VMT Assumptions Percent change in 7.8% 7.8% 7.8% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2030 22,835 22,835 22,835 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2000 new noncompact 2030 24,753 26,831 development −12% −25% Percent reduction in VMT/household in new compact development (continued on next page)
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From page 194... ...
Changes in Energy Use and CO2 Emissions Assumptions Percent change in 58.5% 58.5% 58.5% fleet mpg by 2030 Fleet mpg 2000 19.5 19.5 19.5 2030 30.9 30.9 30.9 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2030 Results −12.0% to +2.1% −12.9% to +0.9% Percent change in fuel use between 2000 and 2030 Fuel use (in billions 2000 114.3 114.3 2030 (1) c of gallons)
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From page 195... ...
2000 1,006 1,006 2030 (2) d 981–1,061 915–980 −1.0% to −1.2% −6.7% to −7.7% Percent change in CO2 emissions from base case −8.9 to −12 −66 to −81 Change in CO2 2030 emissions from base case (millions of metric tons)
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From page 196... ...
Percent of new and 0% 25% 75% replacement units compact New and replacement 2050 0.0–0.0 15.6–25.8 46.8–78.4 units compact (in millions) Changes in VMT Assumptions Percent change in 13.3% 13.3% 13.3% VMT/household in existing development VMT/household 2000 21,187 21,187 21,187 in existing 2050 24,004 24,004 24,004 development Percent change in 8.4% 17.5% VMT/household in new noncompact development 22,967a 24,895a VMT/household in 2000 new noncompact 2050 26,021 28,205 development −12% −25% Percent reduction in VMT/household in new compact development
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From page 197... ...
Changes in Energy Use and CO2 Emissions Assumptions Percent change in 68.7% 68.7% 68.7% fleet mpg by 2050 Fleet mpg 2000 19.5 19.5 19.5 2050 32.9 32.9 32.9 Percent change in 0% 0% 0% carbon content of fuel between 2000 and 2050 Results +0.9% to +28.2% −0.4% to +26% Percent change in fuel use between 2000 and 2050 Fuel use (in billions 2000 114.3 114.3 2050 (1) c of gallons)
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From page 198... ...
2000 1,006 1,006 2050 (2) d 1,051–1,351 963–1,202 −1.3% to −1.7% −8.4% to −11.0% Percent change in CO2 emissions from base case −13 to −22 −88 to −149 Change in CO2 2050 emissions from base case (millions of metric tons)
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From page 199... ...
7,376 lb (3.3 metric tons) savings per unit per year per unit per year Note: Btu = British thermal units; ccf ng = hundred cubic feet of natural gas; kW-h = kilowatt-hours; MFDU = multifamily dwelling unit; SFDU = single-family dwelling unit.
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