Something that's puzzling me for a while is how we could calculate approximately the energy cost of using AES, for a company like Amazon or Google. How likely it is due to the nature of their business model that its an important part of their fixed cost? Considering key generation, encryption and decryption etc of so much data on a daily basis.
Back of the envelope calculation:
According to the World Bank, 2020 internet traffic was 100,000 GB/s. According to this analysis, an Intel i5-8250U CPU uses 2.2 J/GB when using AES-NI to encrypt. Since traffic needs to be both encrypted and decrypted, let's double this to get an energy requirement of 4.4 J/GB.
This works out to approximately 14 terajoules of energy per year.
The US BLS says that February 2022 US electricity costs were $0.137 per kWh.
Therefore, if all internet traffic is encrypted with hardware similar to that referenced above, the total electricity cost to encrypt and decrypt all internet traffic for a year is approximately only $530,000.