Windows 7 helps decrease power consumption across the enterprise. The power management technologies in Windows 7 provide platform and processor efficiencies that reduce power consumption and can help lower energy costs. Windows 7 also can extend battery life for specific scenarios.
Additionally, it provides diagnostic tools that enable original equipments manufacturers (OEMs), independent hardware vendors (IHVs), independent software vendors (ISVs), and IT pros to better manage and troubleshoot power management issues on computers and to extend the battery life for portable computers.
There is a white paper that describes the improvements here.
More information is also available on the Microsoft Environment Web Site.