RESIDENTIAL THERMOSTAT MANAGEMENT PRACTICES: AN INVESTIGATION OF SETBACK REBAVIOR

Transcription

1 RESIDENTIAL THERMOSTAT MANAGEMENT PRACTICES: AN INVESTIGATION OF SETBACK REBAVIOR Carolyn S. Turner and. Kenneth J. Gruber North Carolina A&T State University A survey of residential heating thermostat setback practices was completed by 212 households. The survey focused on identifying the incidence of heating thermostat setback practices as well as the relationship between the practices and thermostat setpoints, number ofdegrees ofsetback, and the presence ofsetback devices. Setback practices were determined from thermostat setpoint data representing four time periods: (1) during the day when no one was at home, (2) during the day when someone was home, (3) during the evening hours while awake, and (4) at night while sleeping. These data were used to derive four setback practices patterns: (1) No Setback, (2) Daytime Only Setback, (3) Nighttime Only Setback, and Combination Daytime and Nighttime Setback. Results indicated that a majority ofhouseholds (65%) employed setback practices for during daytime and/or nighttime periods. Forty-three percent ofthe sample practiced thermostat setback both during the day and night, while an additional 13% and 8%, respectively, made setback adjustments only at night while sleeping or during the day when no onewas home. Households that practiced setback adjusted their thermostats an average ofabout F. A household's baseline setpoint (thermostat setting when no one was at home), was not a reliable determinant of setback differential; households with warmer baselines did not Set back more than those households with cooler baselines. Automatic setback devices were not associated with greater setback activity. Future research will need to address more systematically the regularity of setback behavior and whether setback practices result in meaningful energy savings. INTRODUCTION In recent years interest has grown in determining households' approaches to energy use management. As energy costs continue to follow an unpredictable path, concern remains as to how to best advise consumers on ways to reduce energy costs in their homes. Empirical research has demonstrated that households often have incomplete and/or inaccurate information about the energy use ofthe systems and appliances in their homes (Stern 1986). Efforts designed to improve energy awareness have had mixed success, depending on the motivation level and ability of the audience to implement specific conservation strategies (Costanzo et a ). A major goal of households is to achieve a thermally acceptable and affordable environment for household activities. One basic household energy conservation action to achieve a comfortable environment is thermostat management. Manipulation of thermostat settings is usually one of the first actions taken to reduce energy use (lower energy bills) in that it often precedes measures that require more time and effort (e.g., blocking drafts, covering windows) or that involve more than a modest expenditure (e.g., adding insulation, installing energy efficient windows). Human Dimensions 2.151

2 Because of its simplicity in implementation, thermostat management is a useful indicator of energy-reducing behavior practiced by households (Vine 1986). In any home that has an adjustable thermostat, changes in thermostat setting involve no added financial cost and requires little time or personal effort to implement. Yet, despite its implementation simplicity, thermostat management as an energy conservation behavior is surprisingly complex. This complexity comes from several sources. As a type of energy conservation action, thermostat management represents an example of what Stern and Gardner 1981 classified as "curtailment" behavior. Stern and Gardner (1981) suggested that energy conservation behavior could be divided into two distinct categories: (1) efficiency improvement and (2) curtailment. Efficiency improvements represent actions that involve primarily physical changes to the building shell and to energy delivery systems and equipment, including changes in their design, structure, and function. Efficiency improvements generally involve capital expenditures and require little or no routine intervention from the home's occupants to reduce energy use once installed or activated. Curtailment efforts represent actions that involve more behavioral intervention and response. These efforts include conservation actions that require repeated or continual responses in order to achieve energy reduction. Kempton et al (1985) revised Stem and Gardner's efficiency improvement category to encompass two categories ofactions: (1) efficiency investments and (2) management. Efficiency investments involve a financial investment such as insulation. Management refers to energy use management practices, such as setting back the heating thermostat when the home is unoccupied. Kempton et al. (1985) retained the curtailment category identifying it to include energy actions involving sacrifice, such as tolerating cooler temperatures by lowering the thermostat while persons are awake in the home. Another source that adds to the complexity in interpreting thermostat management behavior are the different understandings people have as to how a thermostatically driven heating/cooling system works (Kempton 1986). Some people believe (correctly) that a thermostat works as a feedback mechanism that cuts the furnace/system on and off in response to the thermostat setting. Others, however, believe (incorrectly) that a thermostat works as a valve and that it controls the rate of heating and cooling. Still, others view (incorrectly) a thermostat, in the case of heating, as a simple switch providing settings of "heat" or "no heat" (Gladhart et al. 1988). These views have important consequences and implications for how households approach thermostat management. Anothersourceinfluencing thermostat management practices is households' response to health and comfort needs. Comfort often predominates up to the point that economy (energy bills) makes it unfeasible to assure comfort through thermostat control (Gladhart et at 1988). The practice of thermostat management is highly subject to influences of individual conditions and characteristics of the home, its heating/cooling systems, and its occupants (Vine 1986). Gladhart et al. (1988) in a study of 10 low-income households found that occupants' thermostat use patterns were dependent on the regularity ofthe household's schedule (when someone would be home), on the outside temperature, and the thermal performance of the housing unit. These investigators found thatwhen homes are better insulated, thermostat settings are better managed in response to changes in outside temperatures. They also found that in the case of heating, low outside temperatures were related to less awareness of thermostat settings, suggesting that occupants' interests in the temperature settings of their heating systems were less important than their personal comfort and perhaps health issues. Despite the interest in thermostat management, one area of investigation that has not received much attention is the practice of thermostat setback. Although many conservation studies list the use of thermostat setback (sometimes in the form of having a clock thermostat installed) as an energy saving strategy (e.g., see Beaulieu, and Miller 1984; Junk et at 1987; Van Der Plight 1985; Vine and Barnes 1988), few studies have examined it as a management behavior that requires maintenance and monitoring. Vine and Barnes (1986) analyzed thermostatsettingpatternsofover 200 homeowners Turner and Gruber

3 in the Pacific Northwest and found that residents set back their heating thermostats at night between 5 F and 6 F. Unfortunately, Vine and Barnes did not report the number of households that actually practiced thermostat setback behavior nor did they report an analysis addressing daytime setback practices. The results of a study by the Honeywell Corporation as reported by Moslander 1980, documented energy savings from thermostat setback practices. Using data collected in 38 cities in nine cold-weather states (Northeast and Midwest), the results indicated that a daytime setback of 10 degrees from 70 F to 60 F saved between 14 to 21 % per year in heating costs, while a nighttime setback of 10 degrees saved between eight and 13% in annual heating costs. By comparison, a five degree setback for both during both daytime when no one is home and at night during sleeping produced savings ranging between 8 and 15%. A five degree setback for during only one of these two time periods produced savings between four and nine percent. The study demonstrated the energy saving potential of setback practices. PURPOSE OF THE STUDY Questions remain concerning the practice and acceptance of thermostat setback behavior. In the present study, thermostat setback behavior was the focus of a mail survey which asked respondents to report heating thermostat setpoint settings and other information related to their heating thermostat use practices. Recent work by Vine and Barnes (1986), Kempton and Krabacher (1987), and Gladhart et al. (1988) suggest that households are good reporters of their thermostat adjustment behavior, despite a tendency to over estimate degree settings. The purpose of this study was to examine some of the more basic questions relating to the prevalence of heating thermostat setback-oils prevalence, amount of setback differential, and relationship of thermostat settings and automatic setback devices to setback differentials. Specifically, the study addressed the following questions: 1. How prevalent is the use of heating thermostat setback practices? 2. When residents practice thermostatsetback,what is the typical number of degrees they adjust their thermostats? 3. Is the practice of thermostat setback related to the temperature settings a household maintains when someone is home during the day and at night? 4. For those households that practice setback, what is the relationship between the base temperature setting (when they are in the home and awake) and the number of degrees they set back their thermostats? 5. Do households that have an automatic thermostat setback device employ different setback practices than households without such devices? METHODOLOGY Thermostat setting and related data were collected through a mail survey. Survey respondents were selected using a randomized systematic selection procedure from the phone book for Guilford Countyand surrounding areas. The survey collection methodology followed Dillman's Total Design Method (1978). A total of 534 surveys were mailed, 30 were returned notdeliverable. Completed and usable surveys were obtained from 212 households. This represents a completed response rate of 42%. Thermostat Management Data Respondents identified thermostat setpoints for four different time periods: Time (1): During the day when no onewas home Time (2): During the day when someone was home Time (3): Duringthe eveninghours while awake Time (4): At night while sleeping From these four reported thermostat settings, the following heating thermostat setback practices were derived: Human Dimensions 2.153

4 1. Daytime thermostat setback--the difference between reported temperatures when someone is in the home during the day and when no one is in the home during the day (Time 2 minus Time 1). 2. Nighttime thermostat setback--the difference between reported temperatures when someone is in the home during the evening and at night when the household is asleep (Time 4 minus Time 3). A positive setback status was assigned if either calculation produced a temperature differential greater than O. From the above calculations, four setback practice groups were determined: (1) No Setback, (2) Daytime Only Setback, (3) Nighttime Only Setback, and (4) Combination Setback (Daytime and Nighttime). RESULTS Thermostat Setback Pra.ctices a.nd Thermostat Setpoint Settings Mean setpoint temperature settings for the four time periods by household setback practice groups are presented in Table 1. As shown in the table, approximately two-thirds (65%) of the households were determined to employ either daytime, nighttime, or both daytime and nighttime setback. About one-tenth of the sample practiced either only daytime (8%) or nighttime (13%) setback. Almost one-half (43%) were found to setback their thermostats both during the day and at night. Comparative analysis ofthe mean thermostat setting setpoints by the setback practice groups revealed significant (using a.05 alpha level) temperature setting differences among the setback practices groups for each time period. Post-hoc comparisons were made using the Tukey test with harmonic means computed for each paired comparison. Households that set back their thermostats during the day when no one was at home (the Daytime Only and Combination Setback groups) maintained significantly lower thermostat settings than did their No Setback and Nighttime Only Setback counterparts. C.A)mparison of thermostat settings for the time period of during the day when someone was at home yielded a significant difference between the Daytime Only Setback group and the No Setback group. The Daytime Only Setback households maintained significantly higher thermostat settings than did the No Setback households. For the evening while awake time period, the Combination Setback group was found to set their thermostat settings at a significantly higher setpoint than did the No Setback group. No other comparisons were significantly different (at the.05 alpha level). For the time period, at night while sleeping, the two groups that set back their thermostats at night, the Nighttime Setback Only and the Combination Setback, had significantly lower nighttime thermostat settings than did the households that did not practice nighttime setback. Finally, though the comparison of the average for all the time periods did yield a significant overall difference, paired comparisons between groups were not significant. Amount of Thermostat Setback The amount of degree setback for each of the three setback groups is presented in Table 2. Statistical comparisons ofmean degree setback for the daytime and nighttime setback groups yielded no significant differences. On average, daytime setback households made setback adjustments of5.7 F, whereas setback adjustments for the nighttime groups averaged about 5.3 F. Also presented in Table 2 are setback differentials for each setback group broken out by recommended energy efficiency temperature range categories (These categories were developed from a combination of sources including conclusions from previous residential energy research, ASHRAE Standards, and utility companies' recommended thermostat setpoints). Because the number of degrees of setback may be a function of a household's preferred room temperatures, a baseline temperature was defined as the reported thermostat setpoint for the daytime period when someone was at home and at night when awake to represent daytime and nighttime temperature baselines. This provided a means by which setback differentials could be examined in relation to the amount of degree setback likely and practical. The analysis was directed at determining if setback differentials were related to the setpoint from which households set back. As the data in Table 2 show, there is no particular trend or pattern Turner and Gruber

5 Table 1. Mean Temperature Settings By Time Period and Setback Practice Group Setback Practice Group Daytime Nighttime Combination Respondent No Only Only Daytime Setback/ Sample Setback Setback Setback Nighttime Setback (N =212) (N =75) (N = 18) (N =27) (N =92) Time of Day M SO M SO M SO ~ SD F No One Home a,b a,c c,d b,d During the Day Someone Home a a Duri ng the Day In the Evening a a at Home While Awake At Night a,c b,d a,b c,d While Sleeping A11 Time Periods *** 4.32** 4.01** 16.89*** 3.32* Note: *** ** Eo <.001 * Eo <.01 Eo <.05 For each Time of Day comparison, means with same superscripts are significantly different from each other. representingsetbacktemperaturedifferentials being a function ofa higher or lower baseline temperature setting. In other words, regardless of the baseline setpoint, the average setback was about E Self Reported Setback Behavior The data presented to this point represent derived and inferred thermostat setback action based on reported thermostat settings. In this section, ratings data representing reported frequency of use of specific setback actions are presented. The ratings ranged from 1 -- "Never" to 4 -- "Most of the time." In addition to providing descriptive data of household's setback behavior, these data also provide partialconfirmation for the assigned setback practice groups. Mean rating data for the setback actions are presented in Table 3. The data are presented broken down by the four setback practice groups. For purposes of statistical comparison, one-way analysis of variance tests were computed for each set ofratings. Post hoc comparisons were computed using the Tukey test. The alpha level for tests of significance was.05. The results show that significantly different reported levels of use were found for the two actions that represented setback behavior. For the action, "During the Day When No One Is Home Lower the Thermostat Setting," the No Setback group was significantly less likely to report doing that behavior than respondents in the three setback groups. The Nighttime Only Setback group also reported a significantly lower frequency of this Human Dimensions 2.155

6 Table 2. Mean Setback Differentials by Energy Efficiency Temperature Range Categories and Setback Practice Group Setback Practice Group Daytime Nighttime Daytime Combination Nighttime Combination Only Daytime Setbackl Only Daytime Setbackl Setback Nighttime Setback Setback Nighttime Setback Temperature Range M SO n f.1 SO n M SO n M SO n 60 F &Below F F F F & Above All Ranges Daytime Setback Nighttime Setback (N :: 110) (N :: 119) Overall Mean Setback M :: 5.73 M::: 5.28 action than the two groups that were identified as users of daytime setback. For the action, "At Night When Going to Sleep Lower the Thermostat Setting,1I the No Setback group again reported a significantly lower rate of use than did the setback group households. The Daytime Only Setback group also reported a significantly lower use rating than either of the two nighttime setback groups. In terms of the rating data providing some confirmation as to the appropriateness of the assignment of the households to the four setback practice groups, the data indicate good correspondence between respondents' reported practices and their assigned setback practices status category. For two actions for which significant differences in use frequency were found (Actions #1 and #4), thepattern of differences was consistent with respondents' derived setback practice group. These actions correspond with daytime and nighttimesetbackbehavior. Actions # 2 and # 3 indicate that respondents generally maintained a constant thermostat setting when they were home during the day and in the evening. Automatic Thermostat Setback Device and Thermostat Setback Behavior Data presenting the relationship between households' having an automatic setback device and their assigned setback practices status category are shown in Table 4. Less than one-fifth (17%) of the sample reported having an automatic thermostat setback device. Ten households reported having a setback device but based on their reported thermostat setpoint data were not identified as employing setback behavior. Only slightly more than one-fourth (26%) of the entire setback group reported having automatic thermostat setback controls. Comparison of each pair of setback groups' setback differential by Turner and Gruber

7 Table 3. Mean Use ofself-reported SetbackActions by SetbackPractice Group Self-Reported Thermostat Setback Action Setback Practice Group Daytime Nighttime Combination No Only Only Daytime Setback/ Setback Setback Setback Nighttime Setback M SO M SO M SO M SO F Lower the Thermostat Setting During the Day When No One Is Home a,b a,c c,d b,d (n :::: 71) (11 ::: 18) (n ::: 26) (n ::: 87) *** Set Thermostat at One Temperature at Home During the Day (11 ::: 72) (11 :: 17) (n :::: 27) (n :::: 88) fils Leave the Thermostat at One Setting In the NS Evening Before Bed (n ::: 70) (n :::: 18) (n :::: 25) (n :::: 86) Lower the Thermostat a,b,c a,d,e b,d c,a Setting At Night When Going to Sleep (n ::: 68) (n :::: 17) (n :: 26) (n :: 87) *** Note: ***E <.001 Means for actions with same superscripts are significantly different from each other. "NS" indicates the comparison of means was not significantly different. setback device status revealed no significant differences in the degree ofsetback between those households with and without setback devices. DISCUSSION The objectives of this paper were to determine the prevalence of thermostat heating setback practices and to examine the relationship between these practices and (a) thermostat setpoints, (b) number of degrees of setback, and (c) the presence of setback devices. Theresults indicate thata high percentage (65%) of the surveyed households practiced thermostat setback The most frequently occurring type of setback was lowering thermostats both during the daytime while away from the home and at nighttime while sleeping (43%). Some households practiced setback only at night (13%) and a smaller group practiced only daytime setback (9%). A substantial portion of the sample adopted some form of this recommended energy efficiency strategy. The average number of degrees of setback was 5.7 P for daytime setback and 5.3 P for nighttime, with a range covering up to 22 F. The findings of the study are similar to the findings of Vine and Barnes (1986) who found that households that Human Dimensions 2.157

8 Table 4. Mean Setback Differentials by Automatic Setback Device Status and Setback Practice Group Setback Practice Group Daytime Nighttime Daytime Combination Nighttime Combination Only Daytime Setback/ Only Daytime Setback! Have an Setback Nighttime Setback Setback Nighttime Setback Automatic Setback Device M SO n!1 SD n M SD!!. M SD n Yes (N :: 35) No (N :: 93) practiced thermostat setback lowered their thermostats 5 to 6 0 F at night. One objective of this paper was to examine the relationship between the four setback practice groups and the thermostat settings reported for each of four time periods. Basically, the analysis shows that significant differences did occur when setback was employed between those practicing setback and those not practicing setback The data show that those practicing setback reported significantly lower thermostat settings for the two critical periods--when no one was home during the day and at night while sleeping. However, as the data further indicate, households in the setback groups maintained thermostat setpoints comparable to the no setbackgroup during time periods ofoccupancy and occupant activity. This suggests as a group, the setback households did not use setback practices to reduce their thermostat settings from higher than average settings. Instead, it appears that the setback groups were conservation minded and were willing to reduce their home's heating during times of day of no occupancy and/or reduced occupant activity. This indicates that the setback groups were not, on the whole, sacrificing or having to tolerate cooler temperatures as a result ofsetback practices. In fact, for two time periods, the temperatures were warmer. It is generally assumed that households that practiced setback are likely to save more energy than those that do not setback However, if the setpoint from which the setback is made is higher than a non-setback household's setting, the net effect may be less certain. It is not clear whether setting back from a higher temperature or leaving the thermostat at an times on a lower level saves more energy. Without analyzing the base temperature in conjunction with the degrees ofsetback, it may be misleading to assume that households that set back save more energy than those who do not. Of those households that practiced setback, the question was asked whether the number of degree~ of setback was related to the baseline temperatures. One might assume that those with high baselines would set back their thermostats a greater number of degrees, but this was not the case. The statistical analysis revealed no significant difference between the groups' baseline temperatures by the number of degrees of setback Regardless of the baseline temperature, on average, the groups were setting back about 5.5 F. Households that employed setback had different temperature preferences, but all apparently adjusted to a five and a half degree differential in the house while they were away and while sleeping at night. Since all groups that practiced setback had about the same degrees of setback, this may indicate different preferences for room temperature but the same tolerance for a change from their baseline temperatures. Significant differences were found in the frequency ratings reported by the respondents to four statements describing setback actions. Those that practiced daytime setback and those that practiced Turner and Gruber

9 combinationdaytime and nighttimesetbackreported more frequently that they lowered the thermostat during the day when no one is at home. Conversely, those that practiced nighttime setback and combination daytime and nighttime setbackreported more frequently that they lowered the thermostat setting at night when going to sleep. For the other two actions, there was no significant difference between the groups. These data indicate two important points. First, the response patterns to the action statements show clear support ofthe assignment ofthe households to their respective setback groups. This is important because group assignment was based only on temperature differentials of reported thermostat setpoints. No other datawere used to assign setback group status. The high congruence of the setback group assignment and self-reported frequency of setback activity suggests that the classification ofthe groups was valid. The second point suggested by the setback behavior data is that households who employ setback practices perceive themselves as doing so quite regularly. Because this study was a mail survey, it was not possible to independently measure respondent reported thermostat settings or setback behavior. Nevertheless, as Vine and Barnes 1986 have reported, residents are generally reliable reporters of their thermostat management actions. Another concern addressed by the study focused on the interrelationship between the presence of an automatic setback device and setback practices. It was e},:pected that the presence of a setback device would be a significant factor associated with the practice of thermostat setback. However, less than a fourth of the households that setback had such devices. Moreover, no significant differences in the number of degrees of setback were found between those households with and without an automatic setback device. AB the data in this study suggest, households are able to regularly practice energy conservation behavior with the benefit of automatic setback devices. The lack of differences in setback differentials between households that had devices and ones that did not further suggests that behavioral conservation practices (management and curtailment) can be integrated in residents' energy management. Further, the data suggest that energy efficient setbackpractices need notbedependenton improvements in technology. CONCLUSIONS The data presented in this paper suggest the following: GIl GIl GIl Most households employed heating thermostat setback practices. Most households practiced a combination of daytime and nighttime setback. Household that practiced setback did not maintain high average thermostat settings (greater that 70 F) while awake in the home. Setback differentials represent substantial setting reductions averaging about 5.5 F. Households employed similar setback differentials for both daytime and nighttime setback. Households were probably reliable reporters of their setback behavior. Having an automatic thermostat setback device was not a major determinant ofsetback practices or setback temperature differentials. DIRECTIONS FORFUTURE RESEARCH Because it was not possible to monitor the thermostat settings or setback behavior of the households included in this study, the conclusions must be tempered by the fact that respondents may have under-reported their thermostat setpoints (see Gladhart et al. 1988; Kempton and Krabacher 1987) and that regularity of setback reporting can only be inferred. Nonetheless, the findings show that many households employed behavioral conservation actions. Future research will need to address more systematically the regularityofsetback behaviorand whether setback practices result in meaningful energy savings compared with households that do not set back their heating thermostats. Human Dimensions 2.159

10 REFERENCES Beaulieu, L. J., and M. K Miller "Factors Contributing to Reported Home Energy Conservation Behavior." Southern Rural Sociology, 2: Costanzo, M., D. Archer, E. Aronson, and T. Pettigrew "Energy Conservation Behavior: The Difficult Path from Information to Action." American Psychologist, 41: Dillman, D. A Mail and Telephone Surveys: The Total Design Method. New York: John Wiley and Sons. Gladhart, P. M., J. S. Weihl, and S. Krabacher "Reported Versus Actual Thermostat Settings: A Management Perspective." Proceedings of the 1988 ACEEE Summer Study on Energy Efficiency in Buildings, Volume 11, pp American Council for an Energy-Efficient Economy, Washington, D.C. Junk, V. W., W. S. Junk, and J. C. Jones "Impact of Energy Audits on Home Energy Consumption." Journal of Consumer Studies and Home Economics, 11: Kempton, W "Two Theories of Home Heat Control." Cognitive Science, 10: Kempton, W., C. K Harris, J. G. Keith, and J. S. Weihl "Do Consumers Know 'What Works' in Energy Conservation?" Marriage andfamily Review, 9: Kempton, W., and S. Krabacher "Thermostat Management: Intensive Interviewing Used to Interpret Instrumentation Data." In W. Kempton and M. Neiman (Eds.), Energy Efficiency: Perspectives on Individual Behavior, pp American Council for an Energy-Efficient Economy, Washington, D. C. Moslander, E "Thermostat Setback: Here's Proof it Works." Popular Science, 10:128. Stern, P. C "Blind Spots in Policy Analysis: What Economics Doesn't Say About Energy Use." Journal of Policy Analysis and Management, 5: Stern,P. C., and G. T. Gardner "Psychological Research and Energy Policy." American Psychologist, 36: VanDerPlight, J "Energy Conservation: Two Easy Ways Out." Journal of Applied Social Psychology, 15:3-15. Vine, E. L "Saving Energy the Easy Way: An Analysis of Thermostat Management." Energy, 11: Vine, E., and B. K Barnes, Lawrence Berkeley Laboratory An Analysis of the Differences Between MonitoredIndoor Temperatures andreported Thermostat Settings. University of California, Berkeley, California. Vine, E., and Barnes, B. K, Lawrence Berkeley Laboratory The Residential Standards Demonstration Program: Occupant Survey Analysis. University of California, Berkeley, California. Weihl, J "Family Schedules and Energy Conservation Behaviors." In W. Kempton and M. Neiman (Eds.), Energy efficiency: Perspectives on Individual Behavior, pp American Council for an Energy-Efficient Economy, Washington, D.C Turner and Gruber