To buy a new expensive hardware it's not a solution.
To spend 150 euro on a motherboard...just to lower the power consumption from 50Euro/year to 40 euro/year...is not so good ideea. More, in my current case, I am able to mount only mATX or bigger motherboard (It's my old desktop casem MASH series from chieftec...)
CA_Steve yes...I know abot the board...but is very hard to get one...and donse't have SATA interfaces (soon I will by 4 more 2Tb hard drives).
The underclock (and this is comming with undervolt)...is getting a quite lower power consumption.
For example, my current CPU:
1GHz, 0.8V The system is drawing 51.1W idle and 55.5W full load
1.4GHz, 0.9V(the lower stable): 54W idle and 62 full load.
Pappnaas after some dig...I found that my bigest problem is the PSU
I have a chieftec gps-400aa-101a 10 years old...and a new no-name PSU is more efficient (without hard drives, the draw power with chieftec is 43.8W, with no-name is 40.3)
I found on xbitlabs site that my PSU (when was new

) have around 65% efficiency under 60W load. Probably now is under 50%. So, is not the case to change the motherboard and cpu. But instead I need to change the PSU. The problem is that I can't find a efficient psu on lower loads (all PSU are efficient above 20% load...and to be above 20% when I draw 50W...I need 250W PSU).
One solution is to put everything that I have in house to draw power form the PSU (the swich, router etc)
But, before change any other hardware...I need to find 250W efficient PSU.
Any sugestions about this?