[shawnz]

Proof-of-work systems don't use ever-increasing amounts of electricity. For example the electricity consumption of Bitcoin is proportional to its price. It won't increase unless the market price of Bitcoin increases, or electricity gets cheaper.

More power consumption also doesn't mean the efficiency is reduced. You would have to quantify the value that users are getting from it to judge the efficiency. If the value goes up with increased power consumption, then the efficiency hasn't changed.