Allocating resources greenly: reducing energy consumption or reducing ecological impact?

Many works concentrate on the energy consumption of data centers, grids and clouds, taking into considerations the trade-off between energy savings and the expected decrease in performances. We argue in this paper that the ecological footprint is not related only to the raw energy consumption but also depends on the production means of the electricity, some being obviously greener than others. We present in this paper proposals to include additional parameters when deciding upon the allocation of tasks to the distributed system.