Monitoring GPU Power Consumption

Is there any way to monitor and record the power consumption of GPU devices in real time - preferably using software?

My goal is to numerically compare the power consumption requirements of a GPU accelerated solution to the equivalent CPU solution.

I have searched online, and it seems that most results are either promotional pages relating to the power consumption of GPUs or specific claims regarding GPU power consumption for a specific problem. I am curious if anyone knows how one can obtain these results.

Bill

Hack a Kill-o-watt!