Energy consumption by information and communication technologies (ICT) has been growing rapidly over recent years. Comparable to the civil aviation domain, the research community now considers ICT energy consumption as a major concern. Several studies report that energy consumption is an issue during all steps of a computer's life, from hardware assemblage, to usage, and dismantling. Research in the area of Green IT has proposed various approaches to save energy at the hardware and software levels. In the context of software, this challenge requires identification of new development methodologies that can help reduce the energy footprint. To tackle this challenge, we propose PowerAPI, a tool to quantify this energy consumption, by providing an application programming interface (API) that monitors, in real-time, the energy consumed at the granularity of a system process.