Bottom line: Less coal because natural gas is cheaper.
Yeah, but at some point that isn't going to be the case. Yes nat.gas is cheaper NOW... but how many THOUSANDS of posts on this forum, claimed "gasoline is going up and up, and will continue going up forever!." Remember that? Remember 2008, when everyone claimed the oil companies were going to drive the price up forever? Remember OPEC, everyone everywhere was screaming about OPEC, and how they were keep pushing the price up until the end of time?
And now where are we? The price is lower today, than it was in the 1920s. 25¢ in 2015 dollars is $2.96. I can fill up for $1.49 /gal. Half the cost of what it was in the 1920s.
My point is, you don't know. You do not know what the future holds.
Natural gas could triple in price. Quadruple in price. You don't know. None of us knows.
And the danger is, what happens when we put all of our energy eggs in one single basket?
Venezuela did this. 70% plus, of their national power production is all hydro power. All one source. Then they had a massive drought, and the water levels were too low, and..........
Power outage plunges most of Venezuela into darkness
Almost the entire country went entirely dark.
Now they have energy rationing.
Venezuela to Begin Nationwide Power Rationing
What do you think is going to happen here in America, if we place all of our energy needs into one source, Nat.Gas, and then we end up with shortages of Nat.Gas?
Will that happen? Who knows. But this is why we need diversity of energy sources. You are begging for trouble if you don't.