Creating Awareness for Efficient Energy Use in Smart Homes
Thomas Rist1), Steffen Wendzel1), Masood Masoodian2), Paul Monigatti2), Elisabeth André3)
1)University of Applied Sciences Augsburg, Augsburg, Germany
2)The University of Waikato, Hamilton, New Zealand
3)University of Augsburg, Augsburg, Germany
Energy advisory services are designed to help habitants of smart homes to learn about their consumption patterns and eventually
save and use energy more efficiently. In this paper we sketch some ideas for energy advisory services and present a layered
software architecture that facilitates the integration of systems for power metering, home automation, and user interface tech-
Efficient use of energy is an ongoing matter of concern to everybody. Regarding the residential
sector of energy end-use some progress towards reducing consumption has been made, for
instance by replacing power-hungry devices such as incandescent light bulbs by fluorescent or
LED light sources. Avoiding waste of energy where possible saves the user money and can
generate positive net effects, such as peak demand reduction which in turn would allow power
line operators to reduce maximum capacity provision. In addition many users do care about
environmental issues and would like to make their own contributions – an effect that may be
circumscribed as the “feel-good” factor. On the other hand, an increasing multitude of new elec-
trical appliances and digital services are offered to the users to make their life more easy, con-
venient, and cozy. In the context of the IT4SE project1 we start from the hypothesis that in a
smart home environment increased comfort and reduced energy consumption are not neces-
sarily mutual exclusive goals. Rather, smart technology may be used to increase users’ aware-
ness of their energy consumption patterns and assist them in smart use of energy in an unob-
Working along this line of research we have examined a number of different technologies in-
cluding equipment for power consumption metering, home automation, and a range of others
that can be categorized as ambient intelligence. In the following sections we present a few ex-
ample systems from each of these categories and discuss them especially with regard to their
user interface issues. Afterwards, we sketch a layered architecture that allows taking advan-
tage of existing components while enabling us to combine and exploit them for new energy
monitoring and usage services in a smart home environment. In addition, we describe some
scenarios to illustrate the application of our architecture.
2 Power Metering
Almost all households with a connection to the power grid have an electricity meter as the
bases for electricity billing. Recently, new types of power usage monitoring (or metering) de-
vices have been introduced to the market, including power sockets with metering/measurement
displays (e.g., www.voltcraft.de), and wireless monitoring units which oversee a number of
power appliances (e.g., www.elv.de, www.currentcost.com). Such monitoring equipment are,
however, designed to provide users with information about the power consumption of specific
appliances. This includes real-time display of consumption, as well as logging usage data over
1 IT4SE is part of the APRA initiative on the establishment of joint research structures between German universities and partners in the Asia
Pacific Research Area (APRA). As all APRA projects, IT4SE is funded by the German Federal Ministry of Education and Research
Fig. 1 Low-cost power
meter with a sparse display
Fig. 2 components of the Current Cost
power usage monitoring system
a certain time period. For example, a user may be interested in how the power usage of their
refrigerator affects their monthly electricity bill, by recording power consumption over a month.
Although low-cost power usage monitoring devices are available in
the market (costing around 10-50 Euro), they have limited function-
ality, sparse information displays, or badly designed user
interaction capabilities. Fig. 1 shows the user interface of a low-
cost metering device (purchased from a German discount store).
Supported functions (e.g., real-time display of power consumption,
or accumulated consumption) can be selected via a toggle button.
A major disadvantage of such low-cost monitoring devices is that
they are “closed” systems, and therefore do not provide any
mechanism for outputting usage data to an external computer
program, nor is it possible to select their functions without having to
operate their physical buttons manually.
For our research work we have been experimenting with a power-
usage monitoring system called Current Cost2 , which provides
external access to measured and recorded power consumption
data. The system configuration comprises three separate type of
components (cf. Fig. 2):
− power sensors: in the form of clamps which are placed
around live power cables;
− transmitters: each of which can process input from up to three power sensors, and use a
wireless connection to transfer data to a monitoring station;
− monitoring unit: a PDA-style device that receives data signals from up to ten different
sources (transmitters) at a refresh rate of 6 seconds. Users can inspect received data on
the PDA screen, or alternatively, use a USB cable to transfer data in a special XML format
(CCXML) to a PC for further processing. In addition, a so-called “Bridge” device is available
that acts as a web server to enable direct access to
XML data via an Internet connection. In this way,
Google's PowerMeter service (Google, 2011) can be
used as a user interface to recorded power con-
The monitoring unit grants access to the total power
consumption recorded at each of the connected transmitter
stations, as well as to each of the individually attached
power sensors. In addition, the monitoring station features
a temperature sensor whose value is included in the
system’s XML output.
Current Cost is devised as a measuring system only, and
therefore, it does not provide any means of controlling
appliances (e.g., to switch them on and off).
3 Home Automation
While it has become commonplace to monitor and maintain modern multi-story office and
commercial buildings using building or facility management systems, automation in private
homes is still in its infancy. However, this may change in the future for a number of reasons.
2 Current Cost is a product of UK-based Current Cost Ltd. (www.currentcost.com)
Fig. 3 components of the HomeMatic
Making private homes smarter in terms of more efficient and responsible use of energy is a
societal challenge and on the political agenda in a growing number of countries. Another driving
force is the manufacturers of home automation systems who view the smart home sector as an
emerging market (e.g., see www.home-automation.org which lists hundreds of different sys-
tems and vendors).
From users’ point of view, home automation can provide many valuable advantages:
− it can increase comfort, for instance by means of sophisticated monitoring and climate con-
− it can help, especially the elderly, to take care of their homes, for example by open-
ing/closing windows and doors using remote control units,
− it can of course also help to save energy, for instance by automatically switching off appli-
ances when they are not needed.
As an example of a commercially available home automation system we have been using in
our research projects is the HomeMatic3 system. The HomeMatic hardware configuration com-
prises the following types of components:
− wireless actuators: in the simplest case an actuator is a power socket that can be re-
motely switched on/off. In addition, there are dedicated actuators comprising a servomotor
to open and close windows, doors, curtains, or heating radiator valves.
− wireless sensors: there are sensors to measure temperature and humidity, sensors that
indicate whether a door or window is closed/open, and motion detector sensors. There are,
however, no sensors to measure energy consumption (e.g. like the Current Cost).
− Central Control Unit (CCU): the CCU executes programs that can take as input data from
attached sensors and output commands to control attached actuators. CCU programming is
done in terms of if-then-else rules on a PC using either a web-based program composer, or
a customized programming environment (such as the Homeputer Studio4 software pack-
age). Once a program has been specified, it gets
compiled and uploaded to the CCU for execution. In the
execution phase no more connection to the PC is
necessary. However, the CCU's built-in web server
allows remote supervision of program execution, even
by means of a smart-phone.
While the HomeMatic system addresses the needs of an
end-user directly, its programming is not an easy task and
requires technical knowledge and good familiarity with
programming environments. However an XML-API has
been made available which allows access to CCU via the
HTTP protocol, thus making it possible to build more
advanced interactive software to use the HomeMatic
4 Ambient Intelligent Environments
The notion of ambient intelligent environments refers to the vision of environments that “... will
react ‘intelligently’ upon our presence and behavior” (cf.Petersen, 2005). Interpretations of
possible meanings of this vision in the context of home environments, often called smart
3 HomeMatic (www.homeatic.com) is a product of eQ-3 AG Germany.
4 Homeputer Studio is a softwarepackage for the HomeMatic system and is distributed by Contronics GmbH Germany (www.contronics.de).
Fig. 4 Nabatztag rabbit in the role of an
homes, are illustrated by a number of prototype smart home installations, including the Philips
HomeLab in Endhoven, and the inHaus laboratory at University of Duisburg-Essen. While
home automation technologies may provide the base for any home environment with intelligent
ambient services, a radically different approach to user interface design has to be followed for
the development of such services. The challenge here is to meet the particular user experience
goals that are of high relevance in home environments. These user experience goals include:
- release the user from the burden of administration and configuration tasks,
- provide information and advice in an unobtrusive but nevertheless effective way,
- learn from user reactions to observable events, and
- adopt automation mechanisms to observed user behavior patterns.
For instance, a standard way of making power-usage monitoring results available to the user
would be a simple number display. However, if the aim is to motivate the users to influence
their behavior towards a more rational use of energy, other means of presentation, might prove
to be more effective. In the next section we discuss some ideas related to user experience of a
smart home that facilitates energy monitoring and efficient usage.
5 Towards Energy Advisory Services in Smart Home Environments
We are currently exploring a number of different use scenarios that combine power usage
monitoring and home automation technologies in order to assist the user in using energy more
intelligently and efficiently.
5.1 Augmented Hall Mirror
The first use-scenario takes its inspiration from the Interactive Mirror developed by Philips Re-
search (cf. www.research.philips.com). This device is a mirror augmented by an information
display and a touch-sensitive surface. In our case we use a modified hall mirror and locate near
the entrance door inside a home environment. Whenever someone approaches the door, the
mirror displays information relevant to the current energy usage, and providing useful informa-
tion and warning to assist the users with saving power. For example when the occupant of the
home is about to leave the house, messages displayed on the mirror might alert the occupant
that certain windows have been left open, or some electrical devices need to be switched off.
5.2 Embodied Energy Advisor
In another case example, we rely on the metaphor of an
embodied character acting in the role of a personal energy
advisor. Our first prototype of such a system uses the so-
called Nabatzag5 rabbit, a kind of electronic toy with
Internet connection. Nabatzag rabbit can play audio clips
that it receives over its Internet connection from different
sources. It also features several colored LEDs and two
movable ears. These components of Nabatzag rabbit can
be used to draw the user's attention it, for instance by
augmenting audio messages with display of non-verbal
Straightforward use cases of this system configuration
include the production of voice utterances relating to
individual energy consumption, e.g., “Did you forget to
close the fridge door?”, or “Today it's going to be a mild
day, shall I turn down the heating while you are away?”.
5 The Nabatztag device is a product of Violet (www.violet.net)
In silent mode, the rabbit’s LEDs might be used to visually communicate status information re-
ceived from a home automation system. For instance, if overall energy consumption is above
average, the energy advisor would get concerned and indicate this by turning on its red LEDs.
However, the design of a believable and intelligent energy advisor is a complex task and re-
quires a considerable amount of research experimentation.
5.3 Collaboration and Competition Games
A particular challenge for the design of assistive and advisory services is the fact that a smart
home may be inhabited by several people, for instance by a family with children. Two questions
arise in this context: (1) is it necessary to track activities related to energy consumption and
saving activities of individuals and if so, what kind of tracking technologies should be used? and
(2) what type of energy advisory services can be designed for groups of users? While technol-
ogy exists for identification purposes (e.g., RFID tags, or camera surveillance) it is doubtful that
people would accept its introduction in their own home. We therefore restrict ourselves to such
group services that do not require behavior and consumption tracking of individuals. As illus-
trated by the following two scenarios, collaborative as well as competitive settings can contrib-
ute to increasing the awareness and smart use of energy. In both scenarios we assume that
each family member has their own energy advisor in the form of a Nabatztag rabbit (cf. Sec.
Collaborative scenario: A somewhat straightforward collaboration scenario generalizes the
above presented embodied energy advisor to a group setting whose members share the goal
of saving energy. Rather than commenting and providing advice on power consumption behav-
ior of an individual, the “family advisor” now comments on aggregated consumption and ob-
served activities of all the house occupants regardless of who was responsible for what. While
this version of the advisor does not require modifications to the technically set-up, the verbal
utterances of the advisor need to be adapted. For instance it might say “Someone forgot to
close the fridge”, or “Hey folks, it’s 25 degrees in here, shall I turn down the heating a bit?”
Competitive scenario: A comparisons of one's own behavior and performance against behav-
ior and performance of others is central to many learning tasks. In a smart home environment
family members may take part in competition games relating to energy saving. For instance, a
family could try to undercut the average power consumption of a family of the same size. A
similar approach was made by the BeAware/Energy Life project for smart phones (cf. BjJaEL,
6 Implementation Framework
As a basis for the implementation of the scenarios sketched above we have designed a layered
architecture, drawing on inspirations from other projects (www.intube.eu, www.ip-symcon.de)
and initiatives (OpenAPC, www.openapc.com) with related aims. The bottom layer of our archi-
tecture is formed by APIs and wrappers which allow us to include hardware components of
different manufactures, such as the Current Cost metering devices, HomeMatic automation
sensors and actuators, and other micro-controllers (e.g., ARDUINO) for additional sensing and
control tasks. The middle layer is to provide network services as well as a unified application
programming interface (API). Sensors and actuators are specified in XML, abstracting away
from the peculiarities of manufacturer-specific communication protocols, and thus increasing
the interoperability between different hardware components. The architecture forms the basis
for the development of our energy advisory applications.
Fig. 5 layered architecture for the development of energy advisory services in the smart home.
7 Conclusion and Future Work
In this paper we presented several design concepts for the development of energy usage moni-
toring and advisory services for smart homes. We have argued that these systems can be de-
veloped using commercially available hardware components such as power usage measure-
ment/metering devices, home automation technologies, and even interactive electronic toys
(e.g. for providing ambient user interfaces to such systems). As component integration is a
technical challenge, we have developed a layered architecture that facilitates integration of
components from a range of manufacturers.
However, there is still a considerable amount of research work to be carried out. Firstly, longi-
tudinal trials should be conducted in order to evaluate acceptance and effectiveness of the ad-
visory services. For example, in a study with elderly people (Klamer and Allouch, 2010) identi-
fied a number of factors that influence the acceptance of Nabatztag companions. Secondly,
there are many technical issues to be addressed further, such as making IT services for the
smart home secure against attacks and unauthorized access.
Björkskog, C. A., Jacucci, G. et al. (2010). EnergyLife: pervasive energy awareness for households, In Proc. of the
12th Ubicomp Conference, Proceedings, 361-362.
Google (2011). www.google.com/powermeter (last accessed March 11 2011).
Klamer, T., Allouch S.B. (2010). Acceptance and Use of a Zoomorphic Robot in a Domestic Setting. In: Proc. of
European Meetings on Cybernetics and Systems Research (EMCSR) 2010
Petersen, M.G. (2005) In: Interactions - Ambient intelligence: exploring our living environment, Vol 12, 44-45.