Unless you have the equipment to directly measure at PCIe slot and extra cable the most convenient method should be to put a power meter directly between wall and computer. That's what I do. Of course you can't actually read the power usage of each component but you can estimate some things and compare. E.g. I did so with CPUs in the same board or GPUs or same GPU with different drivers and operating systems.
Originally Posted by tomtomme
Stop TCPA, stupid software patents and corrupt politicians!