Electricity usage is far from being the only consideration. Even if you added the environmental costs for producing all the computers and mining chips around the world that support what we're doing here in cryptoland, I'm pretty sure fiat still has the larger overall impact on the health of the planet.
On top of that I can add that as the banking system depends on people (a lot of them, that needs a salary, in many mission critical aspects even a fail-safe team made of many people with the same role), it will be always inefficient compared to computer-only systems such as blockchains.
