Recently – motivated by the recent heat where we live – an acquaintance argued that a water cooled computer will not heat up the room as much as an air cooled computer will. His reasoning was that the processors never reach temperatures as high as they would with air cooling, so the room will not absorb as much heat.
This seems flawed to me; the processors have an energy consumption that is regulated by how much processing they do, and that doesn't depend on whether they are air cooled or water cooled. I figured the amount of energy that gets converted to heat should be the same in both cases, the water cooling just doesn't reach temperatures as high as the air cooling because water has a higher capacity for absorbing energy than air does. In the end, the same amount of heat energy would end up in my room in both cases, so I would expect the room to heat up the same, independent of whether we cool our computers with water or air cooling systems.
Which one is right?
Best Answer
There are two parts to this question:
this depends mostly on the fan and pump, I don't have much of an answer here, but in any case the difference will be rather small relative to the total power consumed by the computer.
This is true, and for proof, lets look at a power supply review that tests the efficiency of it both at room temperature, and also inside a hot box - notice how the efficiency is lower inside the hot box ( vs 88.1% at max wattage vs 87.9% at max wattage after a 11º C increase) - again, this is a negligible amount of power (.2%)
What about other components, such as the CPU? that test has been done here, and it seems like an increase of 10º C uses roughly 5W more - which seems significant relative to the others, however one must consider that a good fan & heatsink will be able to match a good liquid cooler to within a couple of degrees see here
So the answer is both will heat up the room by roughly the same amount, and the lead could go to either.