I've recently got hold (for free!) of an old system from a friend based on an AS-Rock K7NF2 motherboard. On it it has a jumper called PS2_USB_PW1. I've never noticed one of these before but from what I've read it controls whether or not +5VSB is used to power devices while the system is in soft off. This can be used for things like Wake-on LAN which I never use.
Soft off power consumption has often been mentioned here before and measuring this system came to 7W. Disabling this jumper brought the number down to 6W. The margin of error may be +/-1W but I have repeated these measurements several times switching the jumper back and forth and it is quite consistent, I can say that using +5VSB to power devices while the system is off wastes power.
Now, assuming that other motherboards may have such a jumper setting, is it worth comparing the effects of this on different boards? Imagine how many systems this effects across the world and the potential power savings add up! Maybe I have solved the impending energy crisis.
I am going to check other systems I have for similar settings and try and minimise the soft off power where possible.