TDP, or thermal design power, basically says how much heat, in watts, a CPU/GPU gives off at maximum. For example, my graphics card has a TDP of 75W. About how many watts in general actually go to render graphics? It obviously depends from card to card (or processor to processor), but I'm looking for a ballpark estimate. I'm guessing the number is very low.
It's an old article but it may help.http://www.tomshardware.com/reviews/geforce-radeon-power,2122.html