Designing Interfaces for Home Energy Users: A Preference Study ...
Designing Interfaces for Home Energy Users: A Preference Study Janelle LaMarche and Olga Sachs Fraunhofer Center for Sustainable Energy Systems 25 First Street, Cambridge, Massachusetts 02141 [email protected]
Abstract. The current study compared user-generated preferences of energy management visualizations to established principles of dashboard design and visual perception. Twenty subjects rated paper prototypes of seven energy web portals according to aesthetic and usability parameters and completed a forcedchoice task on six visual pairs contrasting elements of feedback design. Questions addressed the look of the interface, understanding, usefulness, friendliness, level of visual clutter, and desire to explore. Results revealed robust differences between mean interface ratings across questions, and followup pairwise comparisons further revealed user data was found to be in line with a predetermined pattern of rankings. These results suggest that user-centered design is critical to the implementation and functionality of energy saving visual technologies and can inform future prototypes that maintain effective aesthetics as well as realistic cognition. Keywords: User Experience, Home Energy Management, Feedback, Interface Design, Psychology.
1 Introduction The fields of sustainable energy and media design are becoming increasingly interconnected. Moreover, the success of new home energy technologies depends heavily on usability, consumer acceptance, and participation. How can visual information be used to foster ideas and generate action within the field of energy efficiency? The interactions involved at the human-computer interface may influence both cognitive and behavioral factors involved in the decision-making process [1]. Therefore, when successfully implemented, the visual design and content of an energy web portal may influence a user’s experience and later outcome in terms of energy consumption. The focus of this study was to uncover user preferences for visually presented, energy-based data. Six pairs of visualizations were constructed that contrasted dimensions of feedback design [2]. These contrasted both visual elements (1. Bar vs. pie chart, 2. Horizontal vs. vertical display; data granularity, 3. Ambient vs.technical C. Stephanidis (Ed.): Posters, Part I, HCII 2011, CCIS 173, pp. 58–62, 2011. © Springer-Verlag Berlin Heidelberg 2011
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displays) as well as conceptual elements (4. Projected cost vs. savings, 5. Passive vs. motivational energy tips, 6. Social normative vs. personal goal setting). To investigate the effect of interface design on usability, seven home energy dashboards were amassed from current market or proof of concept products. A dashboard is a display of information needed to achieve one or more objectives and arranged on a single screen so the information can be monitored at a glance [3]. In the energy field, dashboards are becoming increasingly relevant to consumers for realtime feedback on their home energy use. Importantly, all dashboards were analyzed and ranked by the lead researcher according to principles of dashboard design [3], and pre-attentive attributes of visual perception [4]. Thumbnail images of the dashboards, pre-study design notes, and expected pattern of rankings are shown in the Appendix.
2 Method Materials. Materials included laminated pictures of the six visualization pairs as well as paper prototypes of the seven dashboards. For the visual pairs, a forced-choice task was administered (although an answer of ‘both’ was accepted). For the dashboards, subjects completed an aesthetic and usability ratings task assessing the following parameters: Is it nice to look at? Is it easy to understand? Is all of the information provided useful? Would it be useful for you personally? Does it seem friendly? Does it seem cluttered? Does it make you want to explore more? All questions employed a 5-point scale with the anchors ‘Not at all, Slightly, Quite a bit, Very, Extremely.’ Procedure. A total of twenty subjects (Mage 39.5, 10f) were recruited and compensated for their time. All subjects provided informed consent and were instructed to a) choose the visualization from each pair that they liked better and b) rate each of the dashboards according to the questions provided by circling a number on the scale. Participants saw all visual pairs and rated all dashboards. 2.1 Analysis For each visual pair, percentages of choice were calculated. For each question in the ratings task, interfaces were ranked according to their mean ratings across subjects. Table 1. Overall feedback design preferences for the six visual pairs across subjects Pair 1 Pie 65% Bar 30% Both 5%
Pair 2 Horizontal 60% Vertical 40% Monthly 40% Weekly 25% Daily 20% All times 15%
Pair 3 Function 75% Aesthetic 15% Both 10%
Pair 4 Cost 60% Savings 35% Both 5%
Pair 5 Passive tip 50% Active tip 35% Both 15%
Pair 6 Social goal 50% Self goal 40% Both 10%
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J. LaMarche and O. Sachs
Once preliminary analyses were completed, a 7*7 multivariate ANOVA was run with main variables of interest including question (7 levels) and interface (7 levels). Table 2. Interface ranks by question, calculated according to the mean usability ratings across subjects. In addition, the overall expected rank and overall actual rank by mode is also shown. Question Look? Understand? All useful? Useful for you? Friendly? Cluttered? Want to explore? Overall Expected Rank Overall Rank by Mode
N.E.M. 1 3 1 1 2 4 1 1 1
EMonitor 2 1 1 2 1 5 3 2 2
SaveEnergi 5 2 3 3 4 6 2 4 3
Agilewaves 4 4 4 4 3 6 4 3 4
Tendril 2 5 6 6 5 3 4 5 5
TED 6 6 5 5 6 2 6 6 6
Gridpoint 7 7 7 7 7 1 7 7 7
2.2 Results Main effects within subjects revealed a significant effect of question (F(3.02)=4.04, p=.01, Greenhouse-Geisser corrected), interface (F(6)=9.48, p
Abstract. The current study compared user-generated preferences of energy management visualizations to established principles of dashboard design and visual perception. Twenty subjects rated paper prototypes of seven energy web portals according to aesthetic and usability parameters and completed a forcedchoice task on six visual pairs contrasting elements of feedback design. Questions addressed the look of the interface, understanding, usefulness, friendliness, level of visual clutter, and desire to explore. Results revealed robust differences between mean interface ratings across questions, and followup pairwise comparisons further revealed user data was found to be in line with a predetermined pattern of rankings. These results suggest that user-centered design is critical to the implementation and functionality of energy saving visual technologies and can inform future prototypes that maintain effective aesthetics as well as realistic cognition. Keywords: User Experience, Home Energy Management, Feedback, Interface Design, Psychology.
1 Introduction The fields of sustainable energy and media design are becoming increasingly interconnected. Moreover, the success of new home energy technologies depends heavily on usability, consumer acceptance, and participation. How can visual information be used to foster ideas and generate action within the field of energy efficiency? The interactions involved at the human-computer interface may influence both cognitive and behavioral factors involved in the decision-making process [1]. Therefore, when successfully implemented, the visual design and content of an energy web portal may influence a user’s experience and later outcome in terms of energy consumption. The focus of this study was to uncover user preferences for visually presented, energy-based data. Six pairs of visualizations were constructed that contrasted dimensions of feedback design [2]. These contrasted both visual elements (1. Bar vs. pie chart, 2. Horizontal vs. vertical display; data granularity, 3. Ambient vs.technical C. Stephanidis (Ed.): Posters, Part I, HCII 2011, CCIS 173, pp. 58–62, 2011. © Springer-Verlag Berlin Heidelberg 2011
Designing Interfaces for Home Energy Users: A Preference Study
59
displays) as well as conceptual elements (4. Projected cost vs. savings, 5. Passive vs. motivational energy tips, 6. Social normative vs. personal goal setting). To investigate the effect of interface design on usability, seven home energy dashboards were amassed from current market or proof of concept products. A dashboard is a display of information needed to achieve one or more objectives and arranged on a single screen so the information can be monitored at a glance [3]. In the energy field, dashboards are becoming increasingly relevant to consumers for realtime feedback on their home energy use. Importantly, all dashboards were analyzed and ranked by the lead researcher according to principles of dashboard design [3], and pre-attentive attributes of visual perception [4]. Thumbnail images of the dashboards, pre-study design notes, and expected pattern of rankings are shown in the Appendix.
2 Method Materials. Materials included laminated pictures of the six visualization pairs as well as paper prototypes of the seven dashboards. For the visual pairs, a forced-choice task was administered (although an answer of ‘both’ was accepted). For the dashboards, subjects completed an aesthetic and usability ratings task assessing the following parameters: Is it nice to look at? Is it easy to understand? Is all of the information provided useful? Would it be useful for you personally? Does it seem friendly? Does it seem cluttered? Does it make you want to explore more? All questions employed a 5-point scale with the anchors ‘Not at all, Slightly, Quite a bit, Very, Extremely.’ Procedure. A total of twenty subjects (Mage 39.5, 10f) were recruited and compensated for their time. All subjects provided informed consent and were instructed to a) choose the visualization from each pair that they liked better and b) rate each of the dashboards according to the questions provided by circling a number on the scale. Participants saw all visual pairs and rated all dashboards. 2.1 Analysis For each visual pair, percentages of choice were calculated. For each question in the ratings task, interfaces were ranked according to their mean ratings across subjects. Table 1. Overall feedback design preferences for the six visual pairs across subjects Pair 1 Pie 65% Bar 30% Both 5%
Pair 2 Horizontal 60% Vertical 40% Monthly 40% Weekly 25% Daily 20% All times 15%
Pair 3 Function 75% Aesthetic 15% Both 10%
Pair 4 Cost 60% Savings 35% Both 5%
Pair 5 Passive tip 50% Active tip 35% Both 15%
Pair 6 Social goal 50% Self goal 40% Both 10%
60
J. LaMarche and O. Sachs
Once preliminary analyses were completed, a 7*7 multivariate ANOVA was run with main variables of interest including question (7 levels) and interface (7 levels). Table 2. Interface ranks by question, calculated according to the mean usability ratings across subjects. In addition, the overall expected rank and overall actual rank by mode is also shown. Question Look? Understand? All useful? Useful for you? Friendly? Cluttered? Want to explore? Overall Expected Rank Overall Rank by Mode
N.E.M. 1 3 1 1 2 4 1 1 1
EMonitor 2 1 1 2 1 5 3 2 2
SaveEnergi 5 2 3 3 4 6 2 4 3
Agilewaves 4 4 4 4 3 6 4 3 4
Tendril 2 5 6 6 5 3 4 5 5
TED 6 6 5 5 6 2 6 6 6
Gridpoint 7 7 7 7 7 1 7 7 7
2.2 Results Main effects within subjects revealed a significant effect of question (F(3.02)=4.04, p=.01, Greenhouse-Geisser corrected), interface (F(6)=9.48, p
