PoW is the only solution that allows you to make electronic money in P2P work without a trusted third party.

I believe that if it really began to consume a significant amount of energy, it would still be less wasteful than the laborious and resource-intensive traditional banking activities that it would replace. The price will be an order of magnitude less than the billions of bank fees that pay for all these brick buildings, skyscrapers and junk mail for credit cards.

It's ironic if we end up having to choose between economic freedom and conservation of nature.