We measure system-wide power draw from the wall while running the 3DMark Time Spy stress test for 30 minutes.
We also use Nvidia PCAT to measure power draw of the graphics card only, with readings from both the PCIe slot and the PCIe power cables combined into a single figure. This provides us with significantly more accurate data to work with as it is measuring only the GPU power, and not total system power which is a fundamentally imprecise measurement.
Here, we can see the Nitro+'s Performance BIOS averaged 341W under load, a 14W increased compared to the Red Devil's equivalent BIOS. As for the Nitro's Silent BIOS, this proved more frugal, limiting power draw to 311W, though this is still above both the reference card and the Red Devil's Silent BIOS.