In contrast to another box that I have, the Tronsmart ARA X5 with Cherry Trail Z8300, where the ac adapter is 5v/3a, a very small amount of power required to operate.

I quite understand that under very heavy load usage that more power will be required but it made me wonder, when used simply as a media player attached to a TV, what real world power usage the N3150 would have.

My system uses about 36w at the wall under full load (prime 95 + furmark). Now given that my PSU is only at about 10% utilization that means the 400w bronze rated PSU is only operating at about 55-60% efficiency under such a light load. Add to that 2 120mm fans, one intake and one exhaust (exhaust built in to the PSU) and we see a figure of about maybe 25w under full load if the PSU was 100% efficient.

My guess is that standard configuration Beebox would use about 20w under full load given the power brick is much more efficient at that load. Obviously mileage will vary somewhat depending on configuration, adding a mechanical HDD for example could increase that figure significantly. 

The power brick will be designed to accommodate the unit's maximum configuration power draw so 2 RAM modules, an mSATA SSD, mechanical hard disk, wifi card and any additional USB devices you may choose to connect. I would hazard a guess that there would be maybe a 6 - 10w buffer over and above the maximum predicted draw.

I hope this helps.

Thank you for the reply and information, which will always be useful