Not defending banks at all, but they support much more transactions than Bitcoin or any other cryptocurrency. So if we compare the consumption of electricity by each, then we should remember the number of work done as well.
You can't compare the transactions that banks process (that is, centralized transactions, permissioned and so on) with a decentralized transaction system like bitcoin. You are comparing apples to oranges.
All the electricity that the bitcoin network consumes is not wasted, it is a necessity to keep the blockchain safe.
And if LN allows to scale transactions, it may surpass all centralized payment networks. I haven't done the math for this, but intuitively I think would be cheaper compared to all the electricity banks and so on are using. Just imagine the amount of electricity one of these huge buildings consume.
Bitcoin and banks I believe, are still incomparable at this time.
Many people around the globe are still relying with banks while only small percentage are utilizing the bitcoin network.
It's overwhelming to think about how much energy is consuming by the banks everyday.
Yet, we are still very far from the scenario of using the blockchain instead of the conventional method.
But, we are heading to a good future. Banks are starting to see the benefits of blockchain within their system.
Give it a time and most of them are running their system via blockchain.