  In Green Software Development, quantifying the energy footprint of a software
system is one of the most basic activities. This documents provides a
high-level overview of how the energy footprint of a software system can be
estimated to support Green Software Development. We introduce basic concepts in
the area, highlight methodological issues that must be accounted for when
conducting experiments, discuss trade-offs associated with different estimation
approaches, and make some practical considerations. This document aims to be a
starting point for researchers who want to begin conducting work in this area.
