Without subsidies, utility solar and wind are already cheaper than coal. Rooftop solar is still behind, will catch up in 24-36 months.

https://cleantechnica.com/2016/12/25/cost-of-solar-power-vs-...

"The first point is the very basic fact that new wind power and/or solar power plants are typically cheaper than new coal, natural gas, or nuclear power plants — even without any governmental support for solar or wind.

Not only are they typically cheaper — they’re much cheaper in many cases.

Yes, these are levelized cost of energy (LCOE) estimates from Lazard based on various assumptions, and they are averages for the US as a whole rather than prices for specific locations within the US, but the lower estimated costs for these renewables are reflected in the real world as well, where solar & wind accounted for 69% of new capacity additions in 2015, 99% of new capacity additions in Q1 2016, a large portion of new capacity additions in Q2 2016, and probably ~⅔ of new capacity additions for 2016 as a whole."

https://www.lazard.com/media/438038/levelized-cost-of-energy... (warning: pdf)

Even with a reduced capacity factor, if you can shift non-essential loads to when renewables are producing (my pool pump needs to run X hours a day, but I'm happy to wait until the cost of power is low to run it), that's essentially "storage" without needing to pay for storage.

The "intermittency" is an early adoption problem. When you have enough windfarms more uniformly supplying The Grid across the country, this issue will become less of a concern.

What I do see as a big problem is cost. Government subsidies aside, the cost of buying and installing turbines presently is no laughing matter. At scale, solar is rapidly becoming much cheaper to install than wind, which is increasingly becoming reliant on giant 3-5 MW capacity monoliths costing roughly 4-5 million USD a pop--not accounting for installation and maintenance over the long term, and supporting infrastructure and transmission lines to tie the windfarm into The Grid.

I don't believe that analysis is accurate. The demand for coal has been going down for years. The power plants themselves are about as good as it is possible for them to be and they still aren't as efficient on a unit-for-unit basis. The only difference is the installation costs which have been going down for wind and solar over the past 10 years and are still not at peak efficiency.

WRT to your comment on base power, that's the main reason why they haven't stopped using those plants completely, but the problem itself is not insurmountable or dependent on coal. In the U.S. and in SA, they are likely going to switch to Natural Gas peaker plants to manage any periods of instability. And that's one of the big reasons why the Feds in Australia are pushing for that new hydro power in VIC.

TL;DR: coal is on the way out, and the base load is a tough, but fixable problem.

You make a good comment (which I generally agree with), and prompted a thought: How much would it take to change this situation?

For instance, the tax credit is a huge subsidy, and obviously reduces the effective capital cost. But once the capital cost is depreciated after a short period of years, then what does the ongoing marginal cost look like?

If it's low, which I expect it is, then can it be retrofitted with batteries or other technology to store energy?

I don't know the answer, but the lower effective capital cost has to have longer term effects - especially when a coal plant is depreciated over a couple decades.