Power, temps and noise
Yup, that's right, the NUC idles by using 8W at the wall. Accepting a medium-usage scenario of around 15W, the PC would chew through around 50p of electricity of week, used 24/7.
And loading all the cores with Prime95 doesn't push the power consumption up by that much. It behaves very much like a low-power notebook.
Temperatures, too are more than acceptable; the chip is specified with a maximum TDP of 100°C.
The trio of units can barely be heard when idle.
The single CPU-cooling fan does spin faster when under load, understandably, but it sounds louder than the 34.9dB. This has to do with the higher-than-normal pitch that's associated with small fans - Intel's NUC uses a 40mm version. We certainly wouldn't class it as loud but it's definitely audible in a quiet room.