How can we estimate a lower bound for the electrical energy consumed by Bitcoin's Proof of Work (PoW) mechanism? Obviously there is no hard bound, but there are some market laws at work and I think it's possible to give an estimation under some assumptions, but strangely I have not been able to find much like that.
Clarification: I'm specifically looking for something that allows predictions for the future depending on bitcoin price and usage, where mining technology and other factors might have changed. Compare my own answer as an example why I think this is possible, though I feel it could be improved. (Please note that it seems the energy consumption is pretty independent of mining technology ). Of course that kind of answer needs some assumptions - that's perfectly fine.
I think it's important to also have such a lower bound to prepare for what'd happen if the bitcoin price really goes above $100000, as some think, considering that the mining reward is proportional to the bitcoin price, and since we are already (as of 10/2023) around using up 0.4% of the world electricity production (= 15GW, assuming world production is about 30000TWh/year) ... What's your take on that?