Bitcoin has merits. So proof of work, being a part that is currently necessary for it to work has merits.

But the argument that proof-of-work has the merit of incentivizing cheaper energy sources does not stand up.

1. All uses of energy already incentivize the search for cheaper energy. This isn't a novel incentive that proof-of-work provides.

2. But proof-of-work does have a relatively novel disadvantage. It won't just incentivize greater energy uses as prices come down, as in normal supply-demand curves, but must keep up the original and even grow the amount spent on energy.

This would not be a problem in a market without negative externalities, but energy is famously a huge industry that will be struggling with negative externalities for quite some time and at great cost.