What sort of calculation is that? Let's for a moment disregard the fact that banks do much more than just transactions, let's also ignore that there is more then the transaction energy in bitcoin (there are also people working for the miners, producing the hardware etc). Just the comparison between the number of transactions of the banking system (including credit cards) to the number of bitcoin transactions should tell you how different the scales are. There were around daily 400k bitcoin transactions. There were 100 Million credit card transactions per day in the US alone. That would mean if we were to transition to use crypto currencies as our main financial system we'd use more than all the energy we produce worldwide just for bitcoin. So bitcoin looks even worse after doing a bit more of a comparison.
