Mark Aggar, Pat Stemen, and Michael Walsh wrote an article on TechNet Magazine “using group policy to save power”, that gives specific examples as well as fully documents all 35 power management settings covered in Vista.
There are also links to some excellent additional resources included that cover energy efficiency improvements in Vista; make sure to follow them once you finish reading. For example, from the Windows Vista Energy Conservation 'Financial Impact' section, if we calculate (at July 2006 US average energy cost of $0.0931USD per kWh) power savings for just enforcing Sleep settings on PC's:
Annual Per-PC Power Cost Savings Using Sleep (Typical Pentium 4 PC with 17-inch CRT)
760.14 kWh x $0.0931 = $70.77
Annual Per-PC Power Cost Savings Using Sleep (Typical Pentium 4 PC with 17-inch LCD)
597.52 kWh x $0.0931 = $55.63
If you had only 1000 PC's you'd be saving $70,700USD annually. Not to mention that energy costs have climbed significantly since this whitepaper was created (in fact Electric Power Monthly currently puts them at $0.1044USD year to date 2008). The power draw of more advanced chipsets is always on the increase, naturally.