Let's forget about "fair" then, and focus on the allocation. Whether fair or not by someone's definition of "fair", the market system can allocate resources among uncountable federated actors, without spending a significant fraction of those resources on centralized calculations. A zero-price system cannot do that.

There may exist theoretical alternate systems that can allocate more fairly than a market system. If one can do that with unmetered, no-additional-cost-to-the-consumer electricity, I'd be happy to hear about it, as I am not currently aware of any.

Sure, right now unmetered electricity would be a bad idea.