They pull a TON of juice dude just to keep them going. You know what else they pull juice for (on a separate input?). Cooling. It's constant and it's REALLY expensive. Do I have to get into the principles of thermodynamics for the cooling part on this? As long as we can produce the heat onsite within a certain range (and also depending on the system type), we can cool the stacks without drawing a separate load to do the same thing. Also, the remaining waste heat can be used to heat the building, water tanks, etc.