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 PowerColor PCS+ AXR9 390X topped out at 429W in the scene that we use for benchmarking in Battlefield 4, which means it uses about ~55 Watts more power at load than the Radeon R9 290X 4GB card. This is likely due to the factory overclock, three high speed fans and the additional memory used on the frame buffer.
When it comes to Performance Per Watt we can see the PowerColor PCS+ AXR9 390X actually still does better than the Radeon R9 290X!