Someone on the french forum about mining i come from run some tests with a simple rig setup, with 2 x R9 280X
All tests ran with the same frequency etc..
Each algo can be optimized, but for comparison, it's good.
Power at the wall:
Idle
80-90w
scrypt
550W - 2 x 720khs
Scrypt-N
537W - 2 x 350khs
Scrypt-jane
485W- 2 x 133khs
Groestl
271W - 2 x 7 025khs
Myr-G
295W - 2 x 9 920khs
skein
440 W - 2 x 212 500khs
Keccak
430W - 2 x 316 000khs
X11
285W - 2 x 2 080khs
Result : Groestl is the most gpu friendly algo, for power, temp and noise, even better than X11
