I don't have a Thunderbolt, but I do have a Z3801A. It's running off a 48V 1.6A switcher. Idle (no Z3801A) 4W, 6VA Normal (after warmup) 20W, 33VA During warmup 35W, 51VA Measurements are at the wall, using a Kill-A-Watt. They are down around $20 now. -- These are my opinions, not necessarily my employer's. I hate spam.