For testing power consumption, we took our test system and plugged it into a Kill-A-Watt power meter. For idle numbers, we allowed the system to idle on the desktop for 15 minutes and took the reading. For load numbers we ran Battlefield 4 at 3840×2160 and recorded the average idle reading and the peak gaming reading on the power meter.
Power Consumption Results: The system with the XFX Double Dissipation Radeon R9 290 installed used 119 Watts and idle and 453 Watts when gaming. With the second card added to the system the idle power consumption increased to 134 Watts and the peak gaming load jumped up to 743 Watts. Our Corsair AX860i digital power supply was able to easily handle this CrossFire setup, so we recommend at least an 850W or greater power supply if you plan on doing a CrossFire setup with two AMD Hawaii GPUs.