And we forgot to consider the full resources needed by banks. Yes, banks handle more transactions than Bitcoin, but banks don't only use energy/computer power for its transactions, what about the storages needed, what about the indirect expenses. While your bankster sit down on his chair he does not pedal to produce energy, his office uses energy too, when he goes to toilets he uses energy too, the transport of money, paying the employees, emails sent, letters sent, and so, are something to take in consideration
And at this point, you would have to add also the power consumption done by exchanges, online wallets, payment gateways ASIC manufacturers, nodes,
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That's right, but on the other hand I think it's important to note that Bitcoin network doesn't need so many nodes as it has today to perform all the today's transactions and much more. I know some people think that the more transactions in the network the higher the difficulty, but that's not the case. The difficulty is rising with more miners joining the network, and although we can't forbid people mine BTC if they want to, for fairness' sake we must say that the network doesn't need so many of them. I think it's important for understanding the advantages of the blockchain technology in general.
A large number of nodes are also required to keep the network safe
Miners are needed as long as POW exists, the more the better and if they are distinct individuals and companies even better, there is no debate here.
The problem most people don't understand is that bitcoin mining can't be compared to anything else.
It's pretty simple, there are 1800 coins mined each day worth ~ 6700 $ plus rewards.
No matter how many transactions, no matter how "efficient" miners get, they will compete for this sum.
And if their business runs on electricity costs being 80% of the revenue, miners will consume up to 80% (or 9 millions$ of this ) in electricity.
If Bitcoin reaches 67k$ they will burn each day 90 million in electricity and if it goes to 67$ only 90k$ worth.
Those will be the numbers, no matter how many transactions there are or how efficient miners will be or how green the energy is.
Banks don't work like this, banks follow the number of customers. If a branch is overwhelmed by customers they open a new one in the area, if it's deserted it gets closed down.