It seems to me there should be a standard developed for measuring power use similar to the way the EPA measures mileage. Create a standard, or maybe even three standards for different types of users, taking into consideration that processors that do more work allow you to work faster. From such test a user could have a fairly accurate idea of the power use he or she should expect to see. For example such a test can consist of:

Total time with computer on: 8 hours.
Standby time: 2 hours.
Game time: 1 hour.
Using office applications while also browsing the web: 3 hours.
Idle time: 2 hours.

Just throwing this out there.... hopefully someone will see it and latch on to this idea.