Sustainable energy is hands down one of the biggest challenges of our times. As the EU sets its focus to reach its 2030 and 2050 goals, the importance of energy efficiency for energy consumers/prosumers becomes prevalent. Over the years, a lot of different approaches have been followed to engage end-users and affect energy-related occupant behaviour towards improving energy efficiency results and long term behaviour changes. This work presents the SIT4Energy user-centered approach for tertiary buildings that delivers an end-to-end solution that takes into consideration a set of tools and models for successfully engaging and affecting the end-user’s energy-related behaviour. Starting from appropriate user profiling models for energy-related behaviour models and an explainable recommendation engine, to on the fly human activity tracking and micro-moments detection on mobile devices, a set of recommendations are delivered to the end-users through a mobile device, presenting valuable information with user-tailored context and on the optimal timing. The overall solution is clearly documented, whereas real-life results are presented from the deployment in offices in a university building. From the evaluation performed it is clearly depicted that a positive impact has been achieved both in terms of energy efficiency as well as energy-related behaviour.