I wanted to add some DPS-2000BB efficiency numbers to this thread, as I've recently been measuring DC and AC draw on my S9 at various clock speeds.

Counting 12V cable losses, I'm seeing 88.3 to 88.7% efficiency everywhere from 800W up to 1400W DC. Ignoring cable losses the efficiency is 89.7 to 90%.

This is all at a 208V input voltage... efficiency should be higher with higher input voltage but I haven't been able to test that yet.