[amluto]

Your computer is not doing work (in the thermodynamic sense) that gets stored anywhere in the computer, and it is not transmitting a significant amount of energy out the Ethernet port either. (It is moving some energy out the port, copper or fiber, but it’s likely receiving an almost equal amount back, and the power is question is negligible.)

[quesera]

I think what you're saying is that Max Planck knew a thing or two.

[amluto]

Huh? Maybe Rolf Landauer.

But this is really just conservation of energy or the first law of thermodynamics, and those predate Planck.