what does it mean by power consumption for GPUs?

[OmegaShadow]

at sites like tomshardwares and anandtech when they do a power consumption test for graphic cards they give numbers such as 200 watts under active idle and 250 watts under full load.

does this mean the graphic card consumes 200 watts per hour when idle and 250 watts per hour when full load?

^those are just random figures i put up btw.

 

[Lonyo]

No.
Typically the power consumption listed on most (not all) sites is the system power use.
It usually say this at the top of the chart.
System power load means everything in the case, the GPU, CPU, motherboard, RAM etc (but not the monitor, since that plugs in on its own). It's also not typically a total peak load, but one specific to an application.
The power use of various cards can then be compared relative to all the other cards on the chart from that website. So you can work out how much more power card A uses than card B, for example.

What it doesn't tell you is how much power just the card uses.
Some sites do test this, such as (sometimes) Xbitlabs, for one.
Typically people use TDP (thermal design power) to establish power use of a card, as this gives you a typical peak power use.
For example, the TDP for the HD5850 is 151w, and the HD5870 is 188w, so this is a ballpark figure for how much power the cards will use at most.

It doesn't always match up though, TDP can be above or below real power use, so it gives a ballpark figure. The system power consumption on most review sites also is taken from the wall, so it is higher than the real power draw because a PSU isn't 100% efficient, so while it may be drawing 500w from the wall, only say 450w is being used by all the components because the PSU might be 90% efficient.

This is a chart comparing TDP to actual power draw across some (slightly older) NV cards which shows just the card power consumption, not the system power use.

And here is the Anandtech power consumption using a full system (http://www.anandtech.com/show/2711/9):

As you can see, the GPU uses a lot of power, but nowhere near all of it. So while a GTX285 uses maybe 240w, the total system power use is 320w, meaning 80w is coming from "elsewhere".
Power numbers cannot be easily compared across sites because they will be using different hardware setups and different stress tests to get their power numbers, but as I said at the start, it gives you an idea of relative differences between cards.