The first set of results come from the Lenovo ThinkPad T61 notebook with its Intel Core 2 Duo T9300 "Penryn" processor with NVIDIA Quadro NVS 140M as the key components. The first chart shows the power consumption of Windows 7 Professional Service Pack 1 x64 versus Ubuntu 11.04 x86_64 on this dual-core Intel notebook.
Interestingly, the power consumption for this Core 2 Duo notebook is not too different between Windows 7 and Ubuntu when booting up and then letting each operating system idle at their respective desktop. The only item to note is that the Windows 7 power usage tended to spike more than that of the Ubuntu "Natty Narwhal" release.
During light desktop usage (launching the respective web browser, the file manager, navigating system menus, etc), the power usage was close between Ubuntu 11.04 and Windows 7 on the ThinkPad T61. The only difference is that when the applications were loaded, Ubuntu 11.04 was consuming a few more Watts of power than Microsoft Windows 7 Professional.