Pedro Domingos

If renewables are now so cheap, why do they still need government subsidies and mandates?

Yes, but if renewables are cheaper they should prevail even without externality taxes and subsidies. Unless the problem is that they're worse (e.g., less reliable, hidden costs, etc.).

There's a continuum of uses. When there are externalities, markets do not settle on the optimal set of choices (except in corner solutions). Taxes and subsidies allow the "invisible hand" of decentralized business and consumer choices to settle on the optimal mix of uses.

Yes, and what I'm pointing out is that, since even with these taxes and subsidies renewables are overwhelmingly not being chosen by the market, they're a lot worse than they're made out to be.

Also, the externalities of fossil fuels have been greatly overestimated and those of renewables underestimated, so large subsidies and taxes favoring the latter are bad, but that's a separate point.

Yes, coal is a bad polluter, but natural gas is not. And all costs and benefits of each alternative must be considered. On balance, natural gas is currently a better option than renewables.