U.S. Commercial Buildings Energy Consumption and Intensity Trends: A Decomposition Approach

Transcription

1 U.S. Commercal Buldngs Energy Consumpton and Intensty Trends: A Decomposton Approach by Behjat Hojjat, Ph.D. and Steven H. Wade, Ph.D. Economsts, U.S. Energy Informaton Admnstraton, 1 Independence Avenue, SW, Washngton, D.C Phone: /Fax: /Emal: Behjat.Hojjat@ea.gov Introducton The commercal sector s one of the four major end-use sectors n the Unted States, accountng for 17.7 percent of total prmary energy consumpton n 23 (EIA 2). Between 1989 and 23, U.S. commercal sector energy consumpton grew by 31.4 percent compared wth 2.1 percent n transportaton, 18.7 percent n resdental, and 3.9 percent n ndustral sectors (EIA 2). Consequently, carbon doxde emssons by the commercal sector also grew faster than any other sector durng ths perod. Most energy consumpton n the commercal sector occurs wthn buldngs, for example, n 23, buldngs accounted for about 97 percent of the total. Because of the mportance of commercal buldngs energy use to the envronment and the economy, ths study s undertaken to help provde a better understandng of the factors affectng energy consumpton and ntensty wthn energy usng buldngs n ths sector. Data The U.S. Energy Informaton Admnstraton, Commercal Buldngs Energy Consumpton Survey (CBECS), s the most detaled energy-related data avalable for commercal buldngs and s the man source of data for ths report. 1 Currently conducted quadrennally, CBECS s a natonal-level sample survey of buldngs greater than 1, square feet n sze that devote more than 5 percent of ther floorspace to commercal actvty. 2 CBECS data are developed from a multstage area probablty statstcal sample desgned to provde estmates of natonal and regonal data. CBECS s supported by an extensve questonnare that ncludes a wealth of nformaton coverng buldng characterstcs. CBECS also provdes estmated energy consumpton for several key end uses developed based on regresson 1 A CBECS survey was conducted n 1979, after whch surveys were done trennally from 1983 to 1995 and quadrennally snce Ths study focuses on 1989 through 23 snce prevous surveys dd not provde data on a consstent bass. Furthermore, the estmaton results reported are all based on all buldngs usng energy, and may dffer from the fgures reported on the CBECS webste. 2 The commercal sector conssts of busness establshments and other organzatons that provde servces. The sector ncludes servce busnesses (e.g., retal and wholesale stores, hotels, restaurants), publc and prvate schools, correctonal nsttutons, and relgous and fraternal organzatons. Excluded from the sector are the goods-producng ndustres (e.g., manufacturng, agrculture, mnng, forestry and fsheres, and constructon). 1

2 models relatng energy consumpton to relevant buldng characterstcs. CBECS s most recently avalable for the year A tme-seres analyss of natonal CBECS data from 1989 to 23 s the man focus of ths report. Overvew of Energy Consumpton In 23, CBECS estmates that U.S. commercal buldngs consumed more than 6.5 quadrllon Btu (quads) of ste energy, the sum of electrcty, natural gas, fuel ol and dstrct heat. 4 Commercal buldngs energy consumpton grew faster than the stock of buldngs and floorspace, whch ncreased the aggregate energy ntensty over the 14-year perod. Between1989 and 23 commercal buldngs ste energy ncreased by 1.2 quads or 2.1 percent. 5 Over ths same nterval, the number of buldngs grew by.4 percent and total floorspace by 18.3 percent. Thus, aggregate energy ntensty ncreased by 8.7 percent on a per buldng bass and 1.9 percent on a per square foot bass. Methodology Aggregate energy ntensty as used here s defned as total commercal ste energy consumpton per square foot of total floorspace. Changes n aggregate energy ntensty nclude the effects of three major structural factors: changes n the mx of commercal actvtes (e.g., health care, retal sales, and food servce), the regonal dstrbuton of buldngs, and the average sze of buldngs wthn types and regons. Decomposed ntensty solates changes n energy conservaton and energy effcency from aggregate energy ntensty by separately quantfyng the mpacts of the aforementoned structural effects. Ths study apples a decomposton technque to solate the mpact of the three man components affectng commercal buldngs energy consumpton: actvty, structural changes, and ntensty: actvty s defned as the number of buldngs, three structural factors are analyzed: shfts n the composton of buldng types, the regonal dstrbuton of buldngs across U.S. Census regons, and the average floorspace per buldng wthn regons and types, and 3 The 27 CBECS dd not yeld vald statstcal estmates of buldng counts, energy characterstcs, consumpton, and expenures for the U.S. commercal buldng populaton. Because the data do not meet EIA standards for qualty, credble energy nformaton, nether data tables nor a publc use fle were released. 4 The Btu value of energy at the pont t enters the home, buldng, or establshment, s referred to as delvered or ste energy. It does not nclude losses that occur n the generaton, transmsson, and dstrbuton of energy. 5 For consstency wth the decomposton of energy consumpton changes nto component effects, all reported percentage changes related to decomposton are logarthmc. 2

3 decomposed ntensty s defned as the rato of ste energy consumpton to floorspace area after accountng for the mpacts of structural factors Snce 192, numerous methods have been used for decomposng the effects of changes n underlyng factors as they contrbute to changes n an aggregate concept. The logarthmc mean Dvsa (LMDI) method ntroduced by Ang and Cho (1997) was the frst method to provde a perfect decomposton whch does not leave a resdual term. In the present context, the mpacts of changes n the underlyng factors exactly partton the change n total energy consumpton. Ang, Lu and Chew (23) present a revew of extant methods and use the nomenclature Log Mean Dvsa Index method II (LMDI-II) to descrbe ther 1997 methodology. 6 The results whch follow are based on the LMDI-II method due to ts wde use n the lterature, relatve ease of computaton and perfect parttonng of factor mpacts. Constructon of the decomposton methodology wth notaton for the present context of commercal buldng energy ntensty s descrbed n Appendx B. Factors Affectng Energy Consumpton Buldng Type Most energy consumpton n the commercal sector occurs wthn commercal buldngs. 7 Unlke resdental buldngs, a wde varety of heterogeneous actvtes are performed n commercal buldngs. In 23, CBECS characterzed 1 specfc actvtes and 14 prncpal buldng actvtes. To provde a more manageable analyss and also to be consstent wth the Natonal Energy Modelng System (NEMS), a hgher-level classfcaton nto categores s used. 8 The type of commercal actvty n the buldng nfluences the mx of end use servces provded n a buldng (e.g., water heatng, cookng, lghtng, elevator and escalator transport, medcal magng, etc.) and ultmately how much energy a buldng consumes. In 23, mercantle and servce accounted for the most energy consumpton whle food sales 6 Boyd and Roop (24) demonstrate another perfect decomposton methodology based on the Fscher ndex; however, t s computatonally burdensome wth the requred calculatons expandng factorally wth the number of factors analyzed. 7 Non-buldng energy consumpton ncludes outdoor/street lghtng and muncpal uses (e.g., muncpal water supply and treatment). 8 The eleven actvtes are: assembly, educaton, food servce, food sales, health care (npatent), lodgng, large offces (>5, square feet), small offces (<=5, square feet), mercantle and servce, warehouse, and other. CBECS aggregates actvtes nto 14 prncpal buldng actvtes: educaton, food sales, food servce, health care, lodgng, mercantle, offce, publc assembly, publc order and safety, relgous worshp, servce, warehouse and storage, other, and vacant. To test the senstvty of ntensty estmates to the buldng category choce we performed adonal analyss (Appendx A) by aggregatng to just 5 types based on groupng smlar ntenstes and tryng to get more even numbers of buldngs n each category. We also summarze analyss wth and wthout regons n the appendx table. 3

4 grew faster from 1989 than other buldng types wth respect to energy consumpton. Mercantle and servce buldngs, whch are relatvely less energy ntensve, accounted for 27.2 percent of buldngs, percent of floorspace, and 2.4 percent of total commercal buldngs energy consumpton n 23 (Fgures 1 and 2). On the other hand, health care buldngs, whch are the second most energy ntensve, accounted for.2 percent of buldngs, 2.7 percent of floorspace, and 7.3 percent of energy consumpton. Fgure 1. Dstrbuton of commercal buldngs energy consumpton, number of buldngs, and floorspace by buldng type, 23 Merc / Servce Offce <= 5, SQFT Assembly Warehouse Educaton Food Servce Other Food Sales Lodgng Offce > 5, SQFT Health Care Energy Consumpton Number of Buldngs Floorspace percent Fgure 2. Energy ntensty per square foot by buldng type, 23 Food Servce Health Care Food Sales Offce > 5, SQFT Lodgng Other Merc / Servce Educaton Offce <= 5, SQFT Assembly Warehouse thousand BTU per square foot 9 For consstency wth the decomposton of energy consumpton the shares are computed based on all buldngs usng energy. 4

5 Because energy ntensty across the buldng types vares by more than a factor of 5 (Fgure 2), changes n the composton of buldng types have the potental to greatly mpact the aggregate commercal ntensty. Sze Effects Over the 14-year perod, aggregate average floorspace per buldng grew by 6.8 percent wth substantal varaton n growth rates across buldng types and Census regons (Fgures 3 and 4). The average sze of health care buldngs grew by over 24 percent 1, whle three buldng types experenced reductons n average sze. Wde varaton across Census regons also occurred: the average sze of buldngs n the South grew fastest, by over 2 percent, whle the average sze of buldngs n the Mdwest decreased by more than 5 percent. Fgure 3. Percent change n average floorspace per buldng by type category, 23 Health Care Lodgng Warehouse Merc / Servce Food Servce Assembly Offce > 5, SQFT Other Offce <= 5, SQFT Educaton Food Sales percent 1 Our health care category s for npatent facltes only (versus combned npatent and outpatent n all the publshed CBECS tables, except CBECS 23, whch splt nto subcategores). Inpatent health care s one of the most ntensve energy users, but represents the smallest number of buldngs and thus has relatvely large standard errors compared wth other buldng categores wth larger buldng populatons. However, ths ncrease n floorspace was hghly sgnfcant; by pre-aggregatng further, the unque ntensty features of these types of buldngs would be lost. 5

6 Fgure 4. Percent change n average floorspace per buldng by Census regon, 23 South Northeast West Mdwest percent Fuel Source Changes Over the study perod, electrcty consumpton n commercal buldngs has grown at a faster rate than other energy sources wth the mx shftng away from natural gas and fuel ol (Fgure 5). In 1989 electrcty accounted for 47.6 percent of ste energy consumpton, natural gas 36.8 percent, and fuel ol 6.1 percent. Electrcty contnued to be the man energy source n commercal buldngs throughout the Fgure 5. Fuel shares of total ste energy n U.S. commercal buldngs 1989 and 23 percent Electrcty Natural gas Dstrct Heat Fuel Ol perod. In 23, the share of electrcty ncreased to 54.6 percent, the natural gas share declned to 32.2 percent, and the share of fuel ol declned to 3.5 percent. The share of dstrct heat n 23 was smlar to that of

7 Whle the fuel mx by buldng s not a separate decomposton element, ntensty effects are expected to vary on a fuel-by-fuel bass. To show the fuel-specfc features, separate decompostons are presented for total ste energy, electrcty, and natural gas consumpton. Regonal Dstrbutons Between 1989 and 23, the regonal dstrbuton of buldngs shfted slghtly towards the Mdwest Census regon of the U.S. (Fgure 6). The share of buldngs n the Mdwest ncreased by 15 percent, whereas the shares n the Northeast and South regons declned by 8 percent and 5 percent, respectvely. Ths shft has mplcatons for aggregate energy ntensty snce energy consumpton per square foot vares by regon (Fgure 7). However, as wll be shown later we do not expect the mpact of regonal dstrbuton to be sgnfcant. Fgure 6. Dstrbuton of commercal buldngs by Census regon, 1989, 1995, and 23 5 percent Northeast Mdwest South West In Appendx A we present the decomposton results both wth and wthout a regonal effect. 7

8 Fgure 7. Energy consumpton ntensty by Census regons, 23 and change from mllon Btu per buldng thousand Btu per square foot Northeast Mdwest South West percent change from per buldng per square foot Northeast Mdwest South West Results Decompostons of U.S. commercal buldngs energy consumpton are presented for total ste energy, electrcty and natural gas for both the entre perod and specfcally for 1995 splt nto two subperods. The 1995 survey s close to the mdpont of the nterval and ts choce was further motvated by ts usefulness as a demarcaton pont for the ncreasng prevalence and effectveness of energy effcency 8

9 standards. 12 To focus the dscusson, results for the two sub-perods are provded n a separate secton followng the dscusson for the entre tme perod. Decomposton of Natonal Effects for 23 Total Energy Fgure 8 summarzes the decomposton results at the natonal level for the 1989 to 23 perod durng whch commercal buldngs energy consumpton ncreased by 2.1 percent. The ncrease n the average sze of buldngs was the man drver of ths ncrease n energy consumpton followed by growth n the number of buldngs. Under LMDI-II, there s no dfference between the aggregate and the decomposed effect for the actvty varable, thus growth n the number of buldngs ceters parbus 13 ncreased energy consumpton by.4 percent. The decomposed mpact of floorspace per buldng was 18.9 percent, compared wth the prevously noted 6.8 percent growth n aggregate average sze of buldngs. Ths dsparty ndcates that buldng szes were ncreasng most n the more energy ntensve buldng types and/or regons. The combned effects of the number of buldngs and average sze together would have ncreased energy consumpton n commercal buldngs by 3.3 percent. These two factors forcng toward hgher demand for energy were partally offset by the estmated 9.8 percent reducton n consumpton assocated wth changes n composton of buldng types as well as 14, 15 a declne of 1.1 percent n decomposed ntensty per square foot. The decomposton results n a reversal of the drecton of ntensty effect versus the aggregate ntensty presented n the overvew secton. The decomposton analyss estmates an ntensty declne of 1.1 percent versus the aggregate ntensty growth of 1.9 percent. 12 The Natonal Applance Energy Conservaton Act of 1987 mandated a phase out of magnetcally ballasted commercal fluorescent lghtng after 199 and the Energy Polcy Act of 1992 ncluded a 1994 standard for commercal bolers, furnaces and ar-cononng, as well as further fluorescent lghtng standards begnnng n The effects of these standards are expected to be stronger n our post-1995 nterval as equpment retrements buld over tme. 13 To streamlne the ensung dscusson, whenever ndvdual effects are descrbed they wll refer to ceters parbus conons, meanng all other factors reman unchanged unless otherwse stated. 14 Energy consumpton over the perod of study has also been mpacted by Federal equpment standards, state and local buldng energy codes, Federal and state tax cres, as well as other voluntary programs such as Energy Star buldngs. 15 To test the senstvty of decomposton results to the choce of categores we aggregated buldng types n 5 subcategores based on groupng smlar ntenstes and tryng to get an even number of buldngs n each. The fve types are: warehouse and assembly, small offces and educaton, mercantle and servces, other and lodgng, and food sales and food servces. The results of decomposton usng these 5 categores (wth and wthout regonal effects) are reported n Appendx A. The buldng type attrbutons are ndeed senstve to the choce of categores, but the ntensty results are much more stable and dfferent from the aggregate ntensty (Tables A1 and A2). 9

10 Defnng the reducton n consumpton as the amount of energy that would have been consumed f factors had remaned at ther 1989 levels, the buldng type mx and ntensty effect had large mpacts on energy consumpton, reductons of 2.6 and.3 quads, respectvely. Snce U.S. commercal buldngs consumed 6.5 quads of energy n 23, wthout changes n the buldng type mx and energy ntensty reducton they would have nstead used 9.4 quads, over 4 percent more. Puttng ths amount n further perspectve, t s equal to total natural gas consumpton by U.S. commercal buldngs n 23 (2.9 quads). Fgure 8. Decomposton of percent change n total energy consumpton, 23 percent Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change quads Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change 1

11 Total Electrcty There were sgnfcant dfferences n the energy hstory as well as the decomposton results for electrcty use versus total ste energy. Between 1989 and 23 electrcty consumpton ncreased faster than total energy (Fgure 9), by 33.8 percent compared wth a total ste energy ncrease of 2.1 percent. One of the key reasons for the more rapd growth n electrcty consumpton s the ncreasng number of new mscellaneous electrc end uses as well as ncreasng penetraton of these and more traonal end uses. 16 Aggregate electrcty ntensty ncreased by 15.4 percent between 1989 and 23 versus only 1.9 percent for total ste energy. Fgure 9. Decomposton of total electrcty, 23 percent Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change The decomposed electrcty ntensty effect acted to ncrease energy consumpton, but the effect was roughly 3 percent hgher than the calculated aggregate ntensty change. Ths represents a substantal dfference, wth ntensty ncreasng energy consumpton by.3 percent, nearly as great as the mpact of the growth n the number of commercal buldngs. Ths result s a consequence of the growth and penetraton of mscellaneous electrc end uses. At the same tme, the effect of change n buldng type composton was toward less ntensve types, -6.3 percent, less pronounced than for total ste energy. 16 Mscellaneous equpment ncludes computers and prnters, other offce equpment, medcal magng and dagnostc equpment, etc. For example, n the 1989 CBECS, the use of desktop computers was rare enough that questons concernng ther use were not asked.

12 Natural gas Fgure 1 summarzes the decomposton results for natural gas consumpton. 17 An estmated 35.7 percent of natural gas consumpton n 23 was n the Mdwest. Mercantle and servce, educaton, lodgng, and health care buldngs consumed more than 5 percent of natural gas n 23. Between 1989 and 23 natural gas consumpton grew more slowly than total ste energy or electrcty consumpton, by 6.8 percent (Fgure 1) compared to 2.1 percent and 33.8 percent, respectvely. In ths decomposton the buldng effect s dfferent from the frst two decompostons, snce only a subset of buldngs use natural gas. The mpact of the growth n the number of buldngs usng natural gas s only 7.6 percent versus.4 percent for total ste. Over ths perod, aggregate energy ntensty per square foot of floorspace decreased by 12.6 percent. The decomposton results are also qute dfferent than for the other cases. Perhaps most notable s that the decomposed ntensty exhbts an 18.7 percent declne; ths s almost 5 percent greater than the calculated aggregate ntensty declne and underscores the mportance of quantfyng structural effects nstead of relyng on aggregate statstcs. The natural gas ntensty declne contrasts dramatcally wth the ntensty ncrease of.3 percent for total electrcty consumpton over ths perod the use of energy per square foot n buldngs shfted dramatcally toward electrcty, wth a 1.1 percent declne n decomposed Fgure 1. Decomposton of natural gas, 23 percent Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change total ste energy ntensty. The regonal shft effect was more sgnfcant than was found n ether the total ste energy or the electrcty analyses, accountng for a 2. percent ncrease n natural gas consumpton. 17 For the decomposton of natural gas only buldngs usng natural gas as a fuel were ncluded. 12

13 Ths s consstent wth the shft n locaton of commercal buldngs usng natural gas towards the Mdwest and Northeast wth ncreasng heatng requrements. Converted to energy terms, the natural gas ntensty declne translates nto an estmated reducton n consumpton of.4 quads. Natural gas s mostly used for space heatng, whch was also nfluenced by other factors such as mprovements n energy effcency of buldngs, weather, and fuel prces, not consdered n our analyss. Usng heatng degree-days as a measure of wnter weather, 18 there were 5.6 percent fewer heatng degree days n 23 than 1989 whch would also mply lower ntensty n Real natural gas prces were 26.9 percent hgher n 23 than n 1989, whle electrcty prces declned by 14.8 percent over the same perod. As a possble response to the hgher prces, the purchased effcency of new and replacement natural gas space heatng equpment could ncrease, further reducng the heatng component of ntensty. However, snce heatng equpment can last 3 years or more, a lagged response to the rse n natural gas prces could mpact the replacement of furnaces wth the more effcent unts. As wll be shown later, the mpact of change n ntensty s senstve to the tme perod of analyss. Decomposton of Natonal Effects for Sub-Perods 1995 and Total Energy In ths secton, the 1995 and sub-perods are consdered separately to help n understandng the changes n energy consumpton. The change n energy consumpton was sgnfcantly dfferent between the two perods (Fgure ). Energy consumpton decreased by.2 percent between 1989 and 1995 but grew by 2.4 percent between 1995 and 23. Growth n the frst sub-perod from ncreases n the number of buldngs, regonal dstrbuton and energy ntensty (6.7 percent) was offset by the negatve mpacts of buldng sze and buldng type mx (-7. percent). From 1995 to 23, even though the percentage change n buldng type declned more than sx tmes faster than n the earler subperod, the number of buldngs grew somewhat faster and the average sze of buldngs grew by about 24.6 percent. Energy ntensty declned, contrary to the ncrease durng the 1995 perod. The net of all these effects was an ncrease of 2.4 percent n total energy consumpton durng the latter sub-perod. 18 Heatng degree days s a measure of how cold a locaton was over a perod of tme, relatve to a base temperature. In ths paper t s the number of days temperature was below 65 degrees Fahrenhet n one year. 19 In Hojjat and Wade (212), weather was ncluded as a structural factor n the decomposton of resdental energy consumpton. For commercal buldngs, whch tend to be less weather senstve, the statstcal analyss supportng weather decomposed consumpton s less defntve and not ncorporated as a quantfed effect here. 13

14 Fgure. Decomposton of total energy consumpton, 1995 and percent Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change Total Electrcty The change n electrcty consumpton for was 31.1 percent, compared wth 2.7 percent for 1995 (Fgure 12). As mentoned before, the hgher growth n ntensty durng s lkely partally drven by new and expandng electrc end uses whch offset the mpact of energy Fgure 12. Decomposton of electrcty consumpton, 1995 and percent Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change effcency mprovements. The most sgnfcant change n the latter sub-perod was the 22.9 percent growth n the average sze of buldngs whch was much larger than the negatve mpacts of type, and regon effects. The postve ntensty effect of electrcty was larger n the second sub-perod. 14

15 Natural Gas Despte the declne n energy ntensty n the post-1995 sub-perod, total natural gas consumpton ncreased by 7.6 percent durng ths tme perod (Fgure 13). Ths ncrease was manly due to the 28. percent ncrease n the average sze of buldngs, whch more than offset any other factors that effected decreases n natural gas consumpton. Contrary to the latter perod, natural gas consumpton declned slghtly durng Ths declne n the frst sub-perod stems from declnes n the regon, type, and average sze effects, whch more than offset the postve mpact of the buldng effect. The regon effect n the post-1995 sub-perod was more sgnfcant than for the other two decompostons. Also the ncrease n the number of buldngs usng natural gas n the second sub-perod was smaller than n the frst perod. Fgure 13. Decomposton of natural gas consumpton, 1995 and percent Number of Buldngs Regon Buldng Type Average Sze Energy Intensty Total Change Concluson The results show that change n the mx of the buldng types was the domnant reducng effect for total energy consumpton and total electrcty consumpton, ceters parbus. The reducton n energy consumpton accounted for by the composton of buldng types was roughly equvalent to total natural gas consumpton by U.S. commercal buldngs n 23. Contrastng wth the other two energy consumpton concepts, buldng mx was stll an mportant reducng effect for total natural gas, but ntensty reducton was the domnant effect, roughly three tmes larger than buldng mx. Potental reasons for ths reducton were noted more effcent heatng equpment potentally resultng from 15

16 standards as well as rsng natural gas prces, and lower heatng requrements based on generally warmer weather n 23. When analyzng two sub-perods splt n 1995, we found that an ncrease n the average sze of buldngs n the post-1995 sub-perod had the largest ncreasng effect on energy consumpton. Except for total electrcty consumpton, energy ntensty per square foot declned faster n the second sub-perod, whch could be a reflecton of the ncreasng prevalence and effectveness of energy effcency standards. The postve ntensty effect of electrcty was larger n the second sub-perod. Ths ncreasng ntensty has mplcatons for any polcy amed at sustanablty and reducng carbon doxde. To test the senstvty of decomposton results to the choce of categores we aggregated buldng types n 5 sub-categores. We found that the buldng type attrbutons are ndeed senstve to the choce of categores, but the ntensty results are much more stable as well as sgnfcantly dfferent from the calculated aggregate ntenstes. References Ang, B.W., Lu, F. L., Chew E. P. 23. Perfect Decomposton Technques n Energy and Envronmental Analyss. Energy Polcy 31(14), Ang, B. W., Cho, K., Decomposton of Aggregate Energy and Gas Emsson Intenstes for Industry: A Refned Dvsa Index Method. The Energy Journal 18(3) Ang, B. W., 25. The LMDI Approach to Decomposton Analyss: A Practcal Gude. Energy Polcy 33(7), Boyd, G. A., Roop, J. M., 24. A Note on the Fsher Ideal Index Decomposton for Structural Change n Energy Intensty. The Energy Journal, 5(1), 87-. Hojjat, B., Wade, S.H., 212. U.S. Household Energy Consumpton and Intensty Trends: A Decomposton Approach. Energy Polcy 48, , do: 1.6/j.enpol Schpper L., Howarth, R. B., Geller, H., 199. Unted States Energy Use from 1973 to 1987: The Impacts of Improved Effcency. Annual Revew of Energy 15(1), U.S. Department of Energy 21, Energy Effcency Trends n Resdental and Commercal Buldngs, Prepared by McGraw-Hll Constructon for the U.S. Department of Energy, Offce of Energy Effcency and Renewable Energy, August 21. U.S. Energy Informaton Admnstraton, 2. Annual Energy Revew 2, DOE/EIA-384 (2), Washngton, DC. U.S. Energy Informaton Admnstraton, Commercal Buldngs Energy Consumpton Survey, DOE/EIA- Forms EIA 871A-G (1989), Washngton, DC. U.S. Energy Informaton Admnstraton, Commercal Buldngs Energy Consumpton Survey, DOE/EIA- Forms EIA 871A-G (1995), Washngton, DC. 16

17 U.S. Energy Informaton Admnstraton, 23. Commercal Buldngs Energy Consumpton Survey, DOE/EIA- Forms EIA 871A-G (23), Washngton, DC. 17

18 Appendx A. Adonal Decomposton Results and Data Table A1. Decomposton results by dfferent buldng type categores wth and wthout regons No Regons, Types No Regons, 5 Types Regons, 5 Types Total Energy Percent change Number of Buldngs Regon NA NA NA NA NA NA Buldng Type Average Sze Energy Intensty Total Change Total Electrcty Number of Buldngs Regon NA NA NA NA NA NA Buldng Type Average Sze Energy Intensty Total Change Total Natural Gas Number of Buldngs Regon NA NA NA NA NA NA Buldng Type Average Sze Energy Intensty Total Change Sources: computed based on U.S. Energy Informaton Admnstraton 1989, 1995, and 25 CBECS. Note: NA=Not applcable. 18

19 Table A2. Comparson of aggregate and decomposed energy ntensty by buldng types Ste Energy Ste Electrcty Natural Gas Percent change Aggregate (no decomposton) Buldng Types Buldng Types No Regons, Types No Regons, 5 Types Sources: computed based on U.S. Energy Informaton Admnstraton 1989, 1995, and 25 CBECS. Table A3. Energy consumpton, floorspace, and number of buldngs: 1989, 1995, and Total Energy Consumpton (trllon Btu) 5,333 5,321 6,523 Total Floorspace (mllon square feet) 58,489 57,214 7,23 Number of Buldngs (thousand) 4,121 4,351 4,62 Average Floorspace (thousand square feet) Sources: U.S. Energy Informaton Admnstraton 1989, 1995, and 25 CBECS. 19

20 Appendx B. Development of LMDI-II Methodology As mentoned n the report, we dstngushed among three man components affectng commercal buldngs energy use wthn a Census regon: actvty, structure, and energy ntensty. The decomposton methodology was appled frst to each of the four Census regons to solate the effects of these components. We appled equatons below to each Census regon; U.S. natonal results are developed n a second stage usng an LMDI-II analyss that combnes Census regons. The total energy consumpton for a decomposton ncludng buldng types for each regon can be expressed as: * BD SQFT E E E BD * * BD E (1) 1 BD BD SQFT 1 BD 1 where E = total energy consumpton 2, = represents the types of buldngs, BD = total number of buldngs, Let BD = number of buldng type, SQFT total floorspace of buldng type, E energy consumpton n buldng type, BD S share of buldng type, BD SQFT BD E SQFT F I average floorspace of buldng type, average energy ntensty of buldng type, 2 All of the varables n the followng equatons also pertan to partcular tme perods and have an mplct tme dmenson, t, omtted for ease of notaton untl requred for the decomposton equatons begnnng at expresson (8) below. 2

21 Then expresson (1) can be wrtten as E BD S * F * I (2) 1 The dervatve of Equaton (2) wth respect to tme (applyng the product rule) s de 1 S dbd ds df * F * I BD * F * I BD * S * I BD * S * F di (3) By dvdng both sdes of equaton (3) by E and replacng followng expresson: 1 de E wth d ln E we obtan the d ln E 1 de 1 E E 1 BD * S * F * I 1 BD * S * F * I d ln BD d ln F 1 1 BD * S * F * I BD * S * F * I d ln S d ln I (4) Snce the share of energy n the th buldng type s BD * S * F * I E E E e, (5) The growth rate of energy n contnuous tme can be expressed as the weghted average growth rates of the components d ln E 1 e d ln BD d ln S d ln F d ln I (6) The dscrete approxmaton to expresson (6) between year and t s obtaned by ntegratng both sdes of expresson (6) from year to t, so the percentage change n total energy consumpton between year and t for each Census regon can be wrtten as Et ln( ) E d ln BD t t t t d ln S d ln F e e e 1 d ln I e (7) 21

22 expresson: By applyng the LMDI II method and ntegraton rules to expresson (7) we obtan the followng ln Et BDt w ln number of buldngs effect 21 t E BD 1 S w buldng type effect t t ln 1 S F w average sze effect t t ln 1 F I w energy ntensty effect (8) t t ln 1 I where wt s the log -mean weght specfed as ( e t w t L( e, et) (9) ln e e e t ) and e t = represents the share of energy n the th buldng type at year t L ( e, e t ) = the log-mean weght functon The fnal weghts ( w ) are normalzed to sum to one: * t L( e * t w t (1) 1 L( e, e ), e t ) 21 At the U.S. level, the regon effect s calculated as the dfference between the smple growth n the aggregate number of buldngs and the decomposed number of buldngs effect from the 2-stage LMDI-II analyss for combned regons. 22