I should perhaps note that I did this math using the energy density of anthracite coal, that is, the energy that can be released from a tce.  I didn't count the energy expended in mining and transporting the coal, or the energy that would have been expended had the coal been mined in safer and more responsible ways.  At present the coal industry in the US has one of the worst safety records and some of the most catastrophic environmental costs of any extractive or energy industry.  So if we knew the additional overhead (in BTU or any other unit) for mining and transporting the stuff, and the cost of deferred or shirked cleanup, worker illness, etc., and included all of that, the numbers would look worse.

The difference between theory and practise in practise ...