Hardware dissipates energy because software tells it to. But attributing hardware energy usage to particular software functions is complicated due to distribution, resource sharing, and layering of software. To enable research on energy usage attribution, we have created the Software Energy Footprint Lab. We explain the experimental setup offered by the lab and the measurement and analysis methodology that it supports. We also describe some preliminary results aimed at deciphering hardware dissipation profiles for various types of servers under various forms of software stress. Finally, we provide an outlook of how energy footprint measurements can contribute to a body of knowledge on software-level energy optimization.