I came across powercfg back in January while reading about Windows 7 and had some trouble finding some documentation on it today, so I’m posting it here to make it easier for me to find in the future.
Right now, my favorite part of powercfg in Windows 7 is the ability to check on the battery with the -energy option. With metrics like "Design Capacity" and "Last Full charge”, I’m able to get an idea of how my battery is holding up. By running it on my Dell D630, I discovered that I’ve lost 6% of my battery’s capacity 🙁
Microsoft’s Whitepaper: http://www.microsoft.com/whdc/system/pnppwr/powermgmt/PowerCfg.mspx