Accounting the wrong thing?
I think most people are interested in their battery life when they are measuring their battery life.
Numbers you get while plugged in won't have any relevance to battery life or performance. That even applies to mobile devices, despite their learnings.
In fact, what mobile device manufacturers have learned is that the best way to save power is to ramp up power to complete a non-IO task in as little time as possible then go back to a lower TDP as that is where peak efficiency (rather than minimal consumption) lies.