by E Efficiency · 2008 · Cited by 10 — website at eere.energy/ba/pba/pdfs/epact_sec_110_edst_technical_documentation_2008.pdf. 1. Page 8. 2. Key Findings: Changes in National
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Acknowledgements The Department of Energy (DOE) acknowledges the important contributions made to this study by the principal investigators and primary authorsŠDavid B. Belzer, Ph.D (Pacific Northwest National Laboratory), Stanton W. Hadley (Oak Ridge National Laboratory), and Shih-Miao Chin, Ph.D (Oak Ridge National Laboratory). Jeff Dowd (DOE Office of Energy Efficiency and Renewable Energy) was the DOE project manager, and Margar et Mann (National Renewable Energy Laboratory) provided technical and project management assistance. Two expert panels provided review comments on the study methodologies and made important and generous contributions. 1. Electricity and Daylight Saving Time Panel Œ technical review of electricity econometric modeling: Randy Barcus (Avista Corp) Adrienne Kandel, Ph.D (California Energy Commission) Hendrik Wolff, Ph.D (Uni versity of Washington) 2. Transportation Sector Panel Œ technical review of analytical methods: Harshad Desai (Federal Highway Administration) Paul Leiby, Ph.D (Oak Ridge National Laboratory) John Maples (DOE Energy Information Administration) Art Rypinski (Department of Transportation) Tom White (DOE Office of Polic y and International Affairs) The project team also thanks Darrell Beschen (DOE Office of Energy Efficiency and Renewable Energy), Doug Arent, Ph.D (National Renewable Energy Laboratory), and Bill Babiuch, Ph.D (National Renewable Energy Laboratory) for their helpful management review.
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Executive Summary The Energy Policy Act of 2005 (Pub. L. No. 109-58; EPAct 2005) amended the Uniform Time Act of 1966 (Pub. L. No. 89-387) to increase the portion of the year that is subject to Daylight Saving Time. (15 U.S.C. 260a note) EPAct 2005 extended the duration of Daylight Saving Time in the spring by changing its start date from the first Sunday in April to the second Sunday in March, and in the fall by chan ging its end date from the last Sunday in October to the first Sunday in November. (15 U.S.C. 260a note) EPAct 2005 also called for the Department of Energy to evaluate the impact of Extended Daylight Saving Time on energy consumption in the United States and to submit a report to Congress. (15 U.S.C. 260a note) This report presents the results of impacts of Extended Daylight Saving Time on the national energy consumption in the United States. The key findings are: The total electricity savings of Extended Daylight Saving Time were about 1.3 Tera Watt-hour (TWh). This corresponds to 0.5 per cent per each day of Extended Daylight Saving Time, or 0.03 percent of electricity consumption over the year. In reference, the total 2007 electricity consumption in the United States was 3,900 TWh. In terms of national primary energy consumption, the electricity savings translate to a reduction of 17 Trillion Btu (TBtu) over the spring and fall Extended Daylight Saving Time periods, or roughly 0.02 percent of to tal U.S. energy consumption during 2007 of 101,000 TBtu. During Extended Daylight Saving Time, electricity savings generally occurred over a three- to five-hour period in the evening with small increases in usage during the early- morning hours. On a daily percentage basis, electricity savings were slightly greater during the March (spring) extension of Extended Daylight Saving Time than the November (fall) extension. On a regional ba sis, some southern portions of the United States exhibited slightly smaller impacts of Extended Daylight Saving Time on energy savings compared to the northern regions, a result possibly due to a small, offsetting increase in household air conditioning usage. Changes in national traffic volume and motor gasoline consumption for passenger vehicles in 2007 were determined to be statistically insignificant and therefore, could not be attributed to Extended Daylight Saving Time. i
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Table of Contents Page Executive Summary . . i Table of Contents . .. iii 1. Introduction .. .. 1 2. Key Findings: Changes in National Energy Consumption . 2 3. Analysis Approach .. 11 References .. 15 List of Figures Figure 2-1 Average hourly electrici ty consumption, 2006 and 2007 spring EDST periods, Boston 3 Figure 2-2 Ratio of 2007 average hourly electricity consumption to 2006 average hourly consumption, Boston 3 Figure 3-1 Sixty-seven utilities with 2007 data overlaid on climate zone map. 11 Figure 3-2 Illustration of heuristic approach to estimating impacts, Boston.. 12 List of Tables Table 2-1 Energy Savings by Region from Electricity Reductions Using the Heuristic Method 4 Table 2-2 Morning and Evening Impacts by Utility, Spring EDST.. 5 Table 2-3 Morning and Eveni ng Impacts by Utility, Fall EDST 6 Table 2-4 Two-Week Average Motor Gaso line Consumption before and after DST and EDST for Spring, 1998 to 2007. 8 Table 2-5 Two-Week Average Motor Gaso line Consumption before and after DST and EDST for Fall, 1998 to 2007.. 8 Table 2-6 Results from Sta tistical Comparison of Means.. 8 Table 2-7 Summary Results for Traffic from 3:00 p.m. to 9:00 p.m., Spring. 9 iii
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2. Key Findings: Changes in National Energy Consumption Overall National Energy Consumption Findings Using both heuristic2 and statistical analysis methods for measuri ng the national pattern of electricity changes, the study found: For the heuristic analysis, total savings of el ectricity during the four weeks of EDST time in 2007 was 1.3 TWh and the total primary ener gy saved associated with the changes in electricity consumption was 17 TBtu. For the statistical analysis, total savings of electricity during the four weeks of EDST in 2007 was 1.2 TWh. This also corresponds to a total primary energy savings of 17 TBtu. The statistical variation on this result is ± 40 percent (at a 95 percent level of confidence). The electricity savings are small compared to th e national total for the year, representing about 0.03 percent of the total national electricity consumption of 3,900 TWh in 2007. 3 On a daily basis, the total electricity savings due to EDST was 0.46 to 0. 48 percent per each day of EDST. Electricity savings generally occurred over a period of three to five hours in the evening, offset slightly by small increases in energy consumption in several morning hours Štypically the hours ending at 7:00 a.m. and 8:00 a.m. in the morn ing, and ending 5:00 p.m. th rough 9:00 p.m. in the evening. On a daily percentage basis, electricity savings were slightly greater during the March (spring) extension of DST (0.50 percent) than the November (fall) extension (0.38 percent). Regionally, areas of the southern United States exhibited smaller impacts of EDST compared to areas of the North. The study found: Based on the heuristic analysis, electricity savings in the Sout h as a percent per day were the same as in the North regions, 0.48 percent. Based on the statistical analysis, the average daily percent savings in electricity consumption for the North were 0.51 percent, while in the South the savings were 0.42 percent. There is insufficient statistical evidence that th e EDST period has had any measurable impact on motor gasoline consumption for passenger vehicles or traffic volume in 2007. 2 A pragmatic approach that compares the average changes in th e pattern of electricity consumption between 2006 and 2007 during the periods of EDST in March and November without use of formal modeling. 3 Total net electric load for 2006 was 3,900 TWh as report ed by the North American El ectric Reliability Corporation (NERC). The DOE Energy Information Administration (EIA) has projected the national total net generation for 2007 at 3,990 TWh, while consumer demand was 3,900 TWh. The differences are due to electrical losses, generation for self-use, and imports. 2
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Electricity Findings Summary of results using the heuristic method Available hourly electricity consumption data for periods before and after EDST in 2007 and for comparable periods in 2006 made it possible to examine visually the effect of extended daylight saving time in 2007. The study compared hourly electricity consumption for comparable periods in 2006 and 2007 for 67 regionally-representative electric utilities across the country. As an illustration of this comparison, Figure 2-1 shows the hourly electricity consumptionŠover the 21 days of the spring EDST period in 2007 (March 11 through March 31)Šfor the area around Boston. Also shown is the electricity consumption for the same period in March of 2006. Figure 2-1 shows the average hourly consumption levels for both years. Clearly, the evening consumption in hour 19 (hour ending at 7:00 p.m.) during 2007 is relatively lower than during 2006, and the peak evening consumption in 2007 is shifted during EDST from the hour ending at 7:00 p.m. to the following hour. 1,500 1,700 1,900 2,100 2,300 2,500 2,700 2,900 3,100 3,300 3,500 123456789101112131415161718192021222324 (Clock) Hour Ending MWMarch 12 – April 1, 2006 March 11 – March 31, 2007 Figure 2-1. Average hourly electricity consumption, 2006 and 2007 spring EDST periods, Boston Even more revealing is the ratio of the 2007 to 2006 average consumption during corresponding morning and evening EDST hours. Figure 2-2 illustrates a brief but sharp increase in the ratio of average consumption in the morning hour 7 (6:00 a.m. – 7:00 a.m.) and a prolonged reduction in electricity usage during the evening hours 17 – 21 (5:00 p.m. – 9:00 p.m.). Viewed in this manner, the reduction in electricity consumption during the evening hours appears to more than offset the increase in use during the morning hours. 0.9 0.95 11.05 1.1 123456789101112131415161718192021222324 (Clock) Hour Ending 2007/2006 Ratio Figure 2-2. Ratio of 2007 average hourly electricity consumption to 2006 average hourly consumption, Boston Although the ratios of electricity consumption for so me utilities in this study were not as stable during the middle portion of the day as those in the Boston illustration, all of the electricity consumption curves demonstrated similar patterns. 4 Variations from the clear pattern illustrated in Figure 2-1 either showed increases in morning consumption that were not as distinct or in 4 Appendix D in the supporting Technical Documentation (Belzer, et al., 2008) provides additional examples of spring and fall hourly electricity consumption curv es for 19 utilities across all regions of the country. 3
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some southern regions, increased usage of air conditioning appeared to make the energy reductions during the evening occur later and with less intensity. During the 2007 Extended Daylight Saving Time, th e national average daily electricity savings, based on 16 representative regions of the North American Electric Reliability Corporation (NERC), was 0.48 percent per each day of EDST. This was the same average for the broadly aggregated Northern and Southern macro-regions. See Table 2- 1. The lowest energy savings per day were in the Mid-South regions (0.27 percent, on average), while the greatest was in California (0.93 percent). The national daily average electricity savings were 0.48 percent per each day of EDST. Table 2-1. Energy Savings by Region from El ectricity Reductions Using the Heuristic Method 5NERC Region* Location Savings (GWH) Avg. Savings per Day (%) Primary Energy Savings (TBtu) RFC North 336 0.46% 5.3 NPCC-NY North 49 0.41% 0.7 NPCC-NE North 68 0.68% 0.7 MRO North 58 0.37% 0.9 SERC-GAT North 20 0.36% 0.3 WECC-NWP North 111 0.64% 1.6 WECC-RMP North 19 0.43% 0.3 North Subtotal 660 0.48% 9.9 FRCC South 60 0.40% 0.7 SERC-DEL South 25 0.26% 0.2 SERC-SE South 111 0.67% 1.4 SERC-CEN South 40 0.29% 0.5 SERC-VAC South 114 0.52% 1.4 SPP South 33 0.24% 0.5 TRE South 54 0.29% 0.6 WECC-AZN South 20 0.61% 0.2 WECC-CNV South 172 0.93% 2.1 South Subtotal 629 0.48% 7.4 Total 1,290 0.48% 17.3 *Note: Details on the NERC Regions lis ted are found in Appendix B-1 of the supporting Technical Documentation (Belzer, et al., 2008). Summary of results using the statistical method For the spring 2007 EDST, energy consumption data were collected and analyzed from a core 35 utilities. See Table 2-2. The resulting data were interpolated to calculate the average percentage change in energy consumption during a daily period of two hours in the morning and five hours in the evening Štypically the hours ending at 7:00 a.m. a nd 8:00 a.m. in the morning, and ending 5:00 p.m. through 9:00 p.m. in the evening. 5 The national energy savings from electricity reduction ar e determined by the regional results, which are determined by scaling the individual utilities™ results within each region. Appendix B of the supporting Technical Documentation describes the construction of the weighting factors and calculation of national energy savings. 4
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Table 2-2. Morning and Evening Impacts by Utility, Spring EDST Morning Evening Utility* Average Hourly % Chg. Std. Error 6Average Hourly % Chg. Std. Error Indianapolis Power & Light 2.4% 0.9% -3.8% 1.3% Louisville Gas & Elec 1.7% 1.0% -2.6% 1.3% Dayton Hub Œ PJM 1.6% 0.7% -3.4% 1.1% Duquesne Hub Œ PJM 0.6% 0.6% -2.6% 0.9% No. Illinois Hub Œ PJM 1.9% 0.7% -3.6% 0.8% ERCOT – Coast 0.4% 0.9% -0.8% 1.0% ERCOT – S. Central 0.5% 1.3% -1.7% 1.5% Con Ed – New York 0.9% 0.3% -1.9% 0.5% ISO-NE Œ Connecticut 1.1% 0.6% -3.3% 0.8% ISO-NE – NE Mass (Boston) 1.2% 0.5% -2.9% 0.7% Lincoln Electric System 1.2% 0.8% -3.2% 1.4% Madison Gas & Elec 1.8% 0.5% -2.8% 0.7% Otter Tail Power Co. 4.0% 1.6% -2.5% 1.6% City of Tallahassee 1.6% 1.4% -2.1% 1.3% Gainesville Regional Utility 2.0% 1.3% -1.8% 1.3% Jacksonville Energy Authority 1.4% 1.2% -2.2% 1.5% Entergy Corp. 1.1% 0.8% -1.9% 1.4% Alabama Electric Coop -0.1% 1.9% -1.2% 2.3% Oglethorpe Power Co. 0.7% 1.7% -1.7% 1.8% Electric Power – Chattanooga 0.3% 1.2% -2.8% 1.3% Memphis Light, Gas & Water 1.9% 0.9% -2.2% 1.4% Dominion Hub Œ PJM 0.6% 1.3% -3.1% 1.3% Ameren Control Area 1.7% 0.8% -3.1% 1.1% Kansas City Public Utilities 1.2% 1.0% -1.2% 1.3% Southwestern Publc Service 0.6% 0.7% -1.0% 1.1% Western Farmers Elec Coop -0.2% 1.4% -2.5% 1.7% El Paso Electric 2.6% 0.9% -2.2% 1.0% Public Service of N. Mexico 2.2% 0.6% -4.1% 0.6% California ISO 1.7% 0.5% -4.0% 0.6% Los Angeles DWP 2.4% 0.6% -3.7% 0.9% Avista Corp 1.1% 0.7% -2.8% 0.9% Portland General Electric 0.6% 0.8% -1.9% 0.9% Chelan County PUD 2.1% 0.8% -1.0% 0.8% Black Hills Corporation 1.0% 1.1% -3.5% 1.5% WAPA – Rocky Mountain 1.9% 0.7% -3.3% 0.8% * Note: The utilities listed are a combination of individual utilities (investor-owned or consumer-owned) and regional entities — Independent S ystem Operators, or ISOs. Details are provided in Appendix B.1 of the supporting Technical Documentation (Belzer, et al., 2008). The national average reduction in daily electricity consumption in the spring EDST period was 0.50 percent. There were substantial variations reported among util ities for both the morning and evening hours. Morning impacts ranged from a usag e reduction of 0.2 percent to an increase of 4.0 percent,7 while reductions during the evening hours generally were within the range of 1.0 to 6 “Std Error” is the standard deviation associated with th e estimated change in electric ity use, based upon the results of the statistical model. It is a statistical measure that re flects the uncertainty of the estim ated change with respect to its expected (or average) value (as shown in the highlighted columns of Tables 2-2 and 2-3). 7 The morning increases in usage reflect the compounding impact of factors other than lighting. 5
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