Höjer is professor in Environmental strategies and Futures studies at KTH since 2012. He has mainly been working with Smart sustainable cities and Futures studies for sustainable development with focus on energy use and climate change mitigation. Areas he has been especially involved in are related to digitalization, sustainable cities, transport and buildings. Höjer was heavily involved in developing the Swedish National Strategic Innovation Agenda for Smart sustainable cities, 2013-2014, later becoming the Strategic Innovation Program Viable Cities. He was Director of the Vinnova Excellence centre Centre for Sustainable Communications 2008-2017. Höjer is chair of the Smart society working group of KTH Digital Futures since 2020.