Copyright and Reference Information: This material (preprint, accepted manuscript, or other author-distributable version) is provided to ensure timely dissemination of scholarly work. Copyright and all rights therein are retained by the author(s) and/or other copyright holders. All persons copying this work are expected to adhere to the terms and constraints invoked by these copyrights. This work is for personal use only and may not be redistributed without the explicit permission of the copyright holder. The definite version of this work is published as [·] Andreas Berl and Hermann De Meer. An energy-consumption model of energy-efficient office environments. Future Generation Computer Systems, 2011. See http://www.net.fim.uni- passau.de/papers/Berl2011b for full reference details (BibTeX, XML). An Energy Consumption Model for Virtualized Office Environments Andreas Berl a , Hermann de Meer a a University of Passau, Innstr. 43, Passau, Germany Abstract The increasing cost of energy and the worldwide desire to reduce CO 2 emissions has raised concern about the energy efficiency of information and communication technology. Whilst research has focused on data centres recently, this paper identifies office environments as significant consumers of energy. Office envi- ronments offer a great potential of energy savings, given that office hosts often remain turned on 24 hours per day while being underutilised or even idle. This paper describes a virtualized office environment that virtulizes office resources to achieve an energy-based resource management. The resource management stops idle hosts from consuming resources and consolidates utilised services on office hosts. Particularly, this paper develops an energy consumption model that is able to estimate the energy consumption of hosts and network within virtualized and ordinary office environments. The model is used to prove the energy efficiency of the suggested approach analytically and to evaluate it using a discrete-event simulation. Keywords: Energy consumption model, energy efficiency, office environment, virtualization, consolidation 1. Introduction The energy consumed by data centres runs in the billions of Euros [1, 2]. Therefore, various solutions have been suggested to reduce the need for server hardware and energy consumption. Service virtualiza- tion and consolidation, e.g., are widely applied to data centres today and also cloud computing has been introduced as an inherently energy efficient data centre architecture [3]. However, not only data centre equipment consumes energy within enterprises and public administration. Also end-devices located outside of data centres are contributing to a large portion of the IT-based electricity consumption [4]. According to a report commissioned by the German government [5], the energy consumption of IT equipment in German enterprise office environments summed up to about 6 TWh in 2007. This amounts to 68% of the energy consumption caused by data centre equipment (about 9 TWh) in the same year. These numbers indicate that office environments are a highly lucrative area to save energy. Within office environments, especially, office hosts contribute significantly to the IT related energy consumption. On one hand, there are a high number of such hosts because each employee typically has his own host. On the other hand, office hosts are often turned on without being utilised by a user. Often, office hosts remain turned on 24 hours a day. Even if such hosts are mostly idle (CPU usage of 0%) during the time they are running, it is important to see that they still consume a considerable amount of energy. Measurements that have been performed at the University of Sheffield [6] show that typical office hosts which are idle still consume 49% to 78% of the energy that they need when they are intensely used, Email addresses: berl@uni-passau.de (Andreas Berl), demeer@uni-passau.de (Hermann de Meer) Preprint submitted to Future Generation Computer Systems March 10, 2011