Over the last decades, the use of information and communications technology (ICT) and software systems has exploded, making our lives and work much more efficient. However, besides the benefits that ICT brings us, it also contributes significantly to environmental issues [11, 13], not only because of the electricity consumed by computers, data centres, networks or other ICT utilities but also due to the rapidly growing computation needs of emerging software systems that contribute significantly to ever-increasing energy demands and greenhouse gas emissions [1, 21]. Decreasing ICT operation expenses becomes more and more crucial. How to make ICT greener (i.e. environmentally sustainable) and how to develop greener software have been gaining significant attention [16, 17, 24].