It's possible to see an estimate of how much electricity is being used for bitcoin (obviously not the only currency being mined). Higher prices results in more mining so the amount of electricity varies all the time. Here's a graph showing estimates of energy consumption. I guess you can come up with an estimate because you could have an idea of how much it costs to mine a bitcoin and you would see them entering circulation on the blockchain.
During its peak in 2021 it was using about the same amount of electricity as Norway or Argentina uses in a year (according to a University of Cambridge analysis).
Compared to these amounts the banking system would be using a tiny proportion given that fiat currencies don't need to be mined they are just created by the banks when they issue loans.