We measure system-wide power draw from the wall while running the 3DMark Time Spy stress test for 30 minutes.
Total system power draw hovers about the 420W mark, so a negligible increase over the 6800 XT.
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.
Looking at graphics card-only power draw shows the 6900 XT drawing exactly the same as the 6800 XT – at 298W average over our 30 minute stress test. This is quite remarkable considering the 6900 XT has an extra 512 cores, so it is a testament to the efficient architectural design of RDNA 2.