Interactions - January/February 2012

in Figure 4) to different users to use for a week each. Besides the playful discovery aspect that arises when an interested user is confronted with a consumption display, the PowerSocket was used in creative ways that we did not imagine in the lab. One user reported that he used the pulse visualization to check from a distance if his cellphone was fully charged. Despite their high value in discovering such use cases, the deployment of power-consumption visualization prototypes is difficult. In most countries, the manufactur-ing and installation of anything that is connected to the electric network is strictly regulated and restricted to certified companies and engineers. Testbeds like the E.On 2016 House ( http://www.eon-uk.com/ about/ 2016house.aspx), a replica of an 1930s English semi-detached house, are rare and available to only a small number of researchers. Fortunately, chip manufacturers like NXP have realized this problem and provide easy-to-use wireless solutions ( http://ics.nxp.com/sup-port/design/microcontrollers/smart. metering/) that integrate well into prototypes and do not require any handling of high-voltage equipment.

With a network of outlet-based metering systems, we can also envision all sorts of interesting applications. An integration to social networks could encourage people to challenge their friends to consume less. Smart homes could also challenge their inhabitants to undercut their own consumption or that of their neighbors. Families could discuss who consumes most and if the consumption was necessary. As reported in Laschke et al. [ 9], this can be a strong motivation for behavioral change.

Another factor that should be considered is the power consumption of the display itself. With no

2. broms, L., Katzeff, C., bång, M., nyblom, a., Hjelm, S.I., and Ehrnberger, K. Coffee maker patterns and the design of energy feedback artefacts. Proc. of the 8th ACM Conference on Designing Interactive Systems. aCM, new york, 2010, 93-102. 3. arroyo, E., bonanni, L., and Selker, T. Waterbot: Exploring feedback and persuasive techniques at the sink. CHI ‘05: Proc. of the SIGCHI Conference on Human Factors in Computing Systems. aCM, new york, 2005, 631-639. 4. Froehlich, J., Findlater, L., and Landay, J. The design of eco-feedback technology. CHI ‘10: Proc. of the 28th International Conference on Human Factors in Computing Systems. aCM, new york, 2010, 1999. 5. Petersen, D., Steele, J., and Wilkerson, J. Wattbot: a residential electricity monitoring and feedback system. CHI ‘09: Proc. of the 27th International Conference Extended Abstracts on Human Factors in Computing Systems. aCM, new york, 2009. 6. Gustafsson, a. and Gyllenswärd, M. The power- aware cord: Energy awareness through ambient information display. CHI ‘05 Extended Abstracts on Human Factors in Computing Systems. aCM, new york, 2005, 1423-1426. 7. Chetty, M., Tran, D., and Grinter, r. E. Getting to green: Understanding resource consumption in the home. Ubicomp ‘08: Proc. of the 10th International Conference on Ubiquitous Computing. aCM, new york, 2008, 242-251. 8. Heller, F. and borchers, J. PowerSocket: Towards on-outlet power consumption visualization. CHI EA ‘11: Proc. of the 2011 Annual Conference Extended Abstracts on Human Factors in Computing Systems. aCM, new york, 2010. 9. Laschke, M., Hassenzahl, M., Diefenbach, S., and Tippkämper, M. With a little help from a friend: a shower calendar to save water. CHI ‘11: Proc. of the 2011 Annual Conference Extended Abstracts on Human Factors in Computing Systems. aCM, new york, 2010, 633-646. 10. He, H.a., Greenberg, S., and Huang, E. M. One size does not fit all: applying the transtheoretical model to energy feedback technology design. CHI ‘10: Proc.of the 28th International Conference on Human Factors in Computing Systems. aCM, new york, 2010, 927-936.

load attached, our prototype consumes about 0.7 W, which can be reduced drastically when using dedicated hardware. Nevertheless, the comparison between consumed and saved power is a crucial factor for the credibility of such projects. Indeed, one minute of hair-dryer usage is approximately equivalent to a cellphone charger plugged in without load for a whole week. This is something most people will never have thought about. From the literature and the feedback we received during this project, most people start this kind of reflection when they are given a tool that helps them understand power consumption. Once at the maintenance stage [ 10], the visualization could be turned off and reenabled only if some sensory systems detected that the average consumption had increased. We should clearly address the problem of consumption in our displays, but in the end, what we want to achieve is a change in lifestyle. Our displays may add some minimal consumption, but this is offset by increased awareness and reflection. Once this process has begun, we strongly believe it should not be limited to power consumption, but should also apply to water or gas consumption and other areas of everyday life, resulting in reduced overall energy consumption and a more environmentally sustainable lifestyle.

Acknowledgements We would like to thank our student Wolfgang Kluth for the creation of this wonderful prototype. This work was funded in part by the German B-IT Foundation.

January + February 2012

EndnotEs:

1. Pierce, J., Schiano, D.J., and Paulos, E. Home, habits, and energy: Examining domestic interac-tions and energy consumption. CHI ‘10: Proc.of the 28th International Conference on Human Factors in Computing Systems. aCM, new york, 2010, 1985- 1994.

About thE Authors
Florian Heller is a Ph. D. student in
the Media Computing Group at
r W TH aachen University and just
completed a scholarship at the
b-I T research School. His
research focuses on physical
interaction modalities and embedded devices. For
more information and an overview of other projects,
please visit http://hci.rwth-aachen.de/heller.

Jan borchers is full professor of
computer science and head of the
Media Computing Group at r W TH
aachen University. His research
group explores the field of human-
computer interaction, with a particu-
lar focus on new post-desktop user
interfaces for smart environments; ubiquitous, wear-
able, and physical computing; interactive exhibits; and
time-based media such as audio and video. He can
be found online at http://hci.rwth-aachen.de/borchers.