Are you saying that you don't believe us ....Everybody keeps saying that there is little difference of power consumption between S3 and S4. Is there any documentation where I can find something specific on this topic?...
In both S3 and S4 modes, the only power that is "kept alive" is the +5V SB rail, which is rated at a maximum of 2A. So the maximum power that S3 & S4 could consume is 10W. In both S3 & S4, the NIC and USB ports are kept powered by the +5V SB and the only difference between S3 & S4 in terms of power consumption is that the RAM is kept in a low power state in S3, which consumes very little power (~1W).
Hence, you will find that both S3 & S4 will consume about 2W to 8W (depending upon the number of devices being "kept alive".
HTH ....