I found a power meter in my stuffs, which is probably not very accurate, but should allow me to give an idea of what consumes and costs my Raspberry Pi. I want to take into account the conversion from 240 Volts to 5 Volts.
My power meter is the MPM 50 model of brand IDK.
Due to the low consumption of Rasperry Pi, it is possible that the power meter consumption is significant. According to the manual it consumes less than 2 watts.
The experiment just started, so I have didn't accumulated cumulative consumption yet, but here are the first informations on the instantaneous data given by the device:
I'll try to give regular updates on measured consumption.