If I worked in an industry, and a new competitor came out that was initially more expensive, but killed less people, I'm not sure I'd be that surprised if my work started to dry up in favor of the less deadly alternative(s).

If at least one of the alternatives was cheaper too, then I would surmise the game was up.

If you were an arms manufacturer you would be thoroughly unconcerned.

While your witty retort made me laugh, unless you are suggesting that coal power stations are weapons designed to kill people living near them, I think you are missing the point.

I'm suggesting that, pretty much by definition, externalized costs do not get factored into economic decisions.

Unfortunately for coal, not all of its problems are externalities as much as they used to be. If your customer is paying for it, even if not directly in the price you charge, that can alter their behaviour, as we are seeing around the world.

To the extent that customers actually change their behavior, that is a positive development. I'm not sure the effect size is particularly large.

Efficiency programs have been pretty successful, and the overall trend in power consumption (in the US) is negative for now, which is great. But relatively few people even know what fuels are used to supply their power, so I'm not sure how easily consumers can respond.