With forecasts arguing that by the end of the decade one fifth of the global electricity consumption could be consumed by datacenters alone, charting a path towards sustainable high performance computing is of utmost importance. Emerging workloads such as data science and AI are rapidly becoming mainstream in many areas and are calling for disruptive approaches across the board. This talk will first discuss and report investigations carried out across the years, aimed at understanding and proposing novel approaches from heterogeneous processor architectures to programming models and associated runtimes for bettering energy efficiency of compute systems. The second part of this talk will shift focus to the datacenter infrastructure power consumption and present existing approaches and emerging solutions towards carbon-neutral IT, i.e. rethinking the very concept of a compute infrastructure from the ground up beyond the mere use of renewable energies.