Before reading your comment I did some napkin math using 600W per GPU: 10,000,000,000 / 600 = 16,666,666.66...

With varying consumption/TDP, could be significantly more, could be significantly less, but at least it gives a starting figure. This doesn't account for overhead like energy losses, burst/nominal/sustained, system overhead, and heat removal.

It's easy to see what it could be by looking at Green500.

B200 is 1kW+ TDP ;)