Digitalisation is the innovative use of information and communications technologies, in particular the large-scale rollout of smart devices and sensors, and the use of big data collection and analysis. In the context of meeting the energy savings targets of the European Union and improving the energy efficiency of its buildings, this Joint Research Centre Technical Report looks at the technologies, opportunities and challenges presented by digitalisation for heating and cooling. The report provides real-world examples and highlights key policy initiatives and research projects. Digitalisation in heating and cooling has received less attention than digitalisation in other areas, such as household appliances or transport. Yet heating and cooling accounts for around half of final energy consumption. Therefore it is essential to better understand the potential of digitalisation for these end uses, and the technologies with most relevance, in order to develop appropriate policies and prepare the ground for new investment. By analysing the available literature, it is shown that there is a significant opportunity for energy savings and other benefits. However, there is also a possibility that energy savings might not be as large as expected, for example due to the energy consumption of digital technologies themselves, and there are important risks to be anticipated in other areas (privacy, cybersecurity, the digital divide, etc.). New policies – both energy and digital – could mitigate those risks and ensure that the best technologies and business models prevail.