You can look here
In that test system used 122W but it all depends also on other components. Also remember that GPU can have power spikes when it drain more than average power and can cause shutdown of PSU if it do not have enough headroom.
For these days 400W power supply should be probably min. With such headroom even lower quality PSU should have np to handle it.
EDIT: I could not find exact numbers for card alone probably noone bothered to try to get those numbers so you can go only by TDP which is as was wrote 30 W.