The Austrian definition of monopoly differs from the mainstream one.
Wikipedia on monopoly:
A monopoly (from Greek monos μόνος (alone or single) + polein πωλεῖν (to sell)) exists when a specific person or enterprise is the only supplier of a particular commodity…Monopolies are thus characterized by a lack of economic competition to produce the good or service and a lack of viable substitute goods.[2] The verb “monopolize” refers to the process by which a company gains the ability to raise prices or exclude competitors. In economics, a monopoly is a single seller. In law, a monopoly is a business entity that has significant market power, that is, the power, to charge high prices.
AE defines monopoly the way Wikipedia in the article define a legal monopoly:
A government-granted monopoly or legal monopoly, by contrast, is sanctioned by the state… Patents, copyright, and trademarks are sometimes used as examples of government granted monopolies… The government may also reserve the venture for itself, thus forming a government monopoly.
According to Austrians, as long as there are no laws preventing free entry of anyone who so wishes into a particular market, there is no monopoly in that market. They also argue that the power to charge prices not in keeping with the laws of supply and demand will not exist as long as there is free entry. And this is true even if no one at all actually enters, [except for one company that is the only one in the market].
In the old days, there were plenty of energy companies in competition with each other. It was the govt that granted a monopoly to certain companies.
As for the question if monopolies are always great, or can they be mediocre, the answer, according to Mises in HA, is that they can indeed be mediocre. See Chapter 16, section 6, Monoply Prices. Here’s a small quote from there:
Monopoly is a prerequisite for the emergence of monopoly prices, but it is not the only prerequisite. There is a further condition required, namely a certain shape of the demand curve. The mere existence of monopoly does not mean anything. The publisher of a copyright book is a monopolist. But he may not be able to sell a single copy, no matter how low the price he asks. Not every price at which a monopolist sells a monopolized commodity is a monopoly price. Monopoly prices are only prices at which it is more advantageous for the monopolist to restrict the total amount to be sold than to expand his sales to the limit which a competitive market would allow.