If you said, the miners are near wind-farms, then I would eat up your statement about oversupply. For hydro more or less, that is electricity that could be used for something else but being burnt.

I am not sure about Chinese miners being near hydro-electric some may be and some may be not, but over all its complete waste of energy.

When it comes to energy efficiency nothing beats centralized. I do understand the motivation behind decentralized, but you pay the price!

Hopefully Proof of Stake with reduced power consumption becomes a norm, but I am skeptical.