# The Effects of Augmented Reality Companion on User Engagement in Energy Management Mobile App
## 2 Related Works
### Energy Management with Augmented Reality  
In the energy management context, AR was mainly used for (1) simply visualizing IoT sensor data or (2) presenting a digital twin for data visualization and control interface. For example, [PERSON] et al. [16] developed an AR mobile app that visualized electricity consumption data of appliances collected through IoT sensors in real-time. Data were displayed in AR text and a printed image was used as a marker for positioning the AR text. On the other hand, [PERSON] et al. [33] presented a mobile AR app combined with IoT sensors that displayed energy consumption information and air quality data on a mobile screen. The AR mobile app used image recognition to recognize IoT sensors for AR initialization, and information in AR was provided as text. Unlike [PERSON] et al. [16]'s AR mobile app, [PERSON] et al. [33]'s AR mobile app enabled a remote control on one IoT sensor at a time, whereas [PERSON] et al. [34] extended the remote control for up to five devices. [PERSON] et al. [34] designed an AR mobile app that visualized a building's energy consumption states in an AR map, which was a digital twin of the place in the real-world, which was augmented on a miniature building. While checking the states of energy consumption through their mobile AR app, users could control the power of IoT devices in the place through the AR interface. However, both studies only developed and introduced the UIs without user evaluation regarding either user engagement or perceived usability aspects. As AR technology matured, a need arose to evaluate how AR is perceived and its effect on user engagement. [PERSON] et al. [35] measured 40 university students' perceptions of AR in the self-learning app that was used to enhance their awareness of the appliances' energy efficiency. [PERSON] et al. [35] utilized object recognition and image recognition to identify various-sized appliances, as large appliances were incompatible with their AR mobile app's object detection technique. The energy consumption information was calculated based on a timer, which implied the duration of appliance usage, and a manually assigned power usage value for the identified appliance to provide an energy efficiency performance. Once the calculation was completed, the energy efficiency information was displayed as text with an icon highlighted with different colors depending on the calculated energy efficiency score. Although the energy consumption information was an estimated value instead of sensor-based data, the students assessed that they could gain knowledge about the energy consumption information of each appliance. More than half of students positively perceived the AR mobile app as easy to use, enjoyable, useful, and wanted to use continuously [35]. Instead of estimating energy consumption, [PERSON] et al. [36] used real-world data provided by IoT sensors in a school building for their AR mobile app to enhance the learning experience in a classroom. [PERSON] et al. [36] developed a lab kit alongside an app that helped primary and secondary school students be aware of school energy consumption. The AR mobile app presented virtual texts with line graphs to show the energy consumption states without access to the web portal where all data were available. The user evaluation, which involved 106 primary and secondary school students, identified a positive influence on user engagement with their lab kit and the content delivered through the AR mobile app. However, their research was mainly focused on education and learning effects rather than the influence of AR on user engagement. While the aforementioned AR mobile apps focused on educating users about energy consumption or energy efficiency, [PERSON] et al. [37]'s AR mobile app centered on its functionality to empower users with real-time data. [PERSON] et al. [37] developed a mobile app that provided energy information about kitchen appliances obtained from IoT sensors in AR.