Do we only need to measure the CPU?

[ohuu]

Obviously not right? The GPU can consume significant amounts of energy without flexing the CPU. Other components may also be the similar to GPUs (although probably not to the same extent).

Maybe the best approach is to profile system power consumption with and without the process you are interested in and taking the difference. Some statistical method (something like PCA) would need to be used because power consumption will depend on how those processes are using the CPU not just how many instructions they are executing.