Coal has huge costs that haven't been previously accounted for.

The problem with coal is it is devastating to the environment at every stage: 1) extraction; 2) shipping; 3) burning; 4) storing waste (coal ash).

Old coal ash ponds have leaked and new ones will continue to do so. There is no fail-safe way to store coal ash. When the ash covers an area, taxpayers pay for the cleanup. Burning coal produces acid rain, which eats the paint of your vehicle (guess who pays to fix that).

Reduced air quality causes diseases such as asthma...pretty sure the coal companies don't pay your medical bills. Further, extraction through mountaintop removal completely fills in entire valleys which contaminates surface and ground waters. Contaminated groundwater forces residents to relocate, surface water forces municipalities spend more to clean it to produce safe drinking water...again not payed for by power companies.

In summary, we are already paying a lot for coal, we just don't do it through our power bills.