Additional in relation to what? Legacy systems need hardware and electricity too, people tend to forget this. I'd like to see the math on how much additional hardware is needed, if at all. My suspicion is that there's a lot of redundancy in the current infrastructure because each bank has to maintain their own record, given that they can't trust each other. A trustless and decentralized system, if it became the base layer for interbank payments, might actually reduce resource consumption.