I'm unsure if British Thermal Units are even a measurement these days, but my history as a Human Being on this Planet includes being a qualified gasfitter. As such I know the BTU output relative to the fuel ingested is mostly perfect when you burn coal. I doubt anything except neuclear power would come anywhere near it's efficiency. Wind farms, solar, wave farms are a myth in economic terms.
And guess what?
Australia has enough coal to meet our BTU needs for the next six million years. Brave figures I hear you say, but none worse than the alternative vegans answer to a problem that doesn't exist.
Probably a conservative guess compared with "the science" that "is in" and "models" show that shoving a big wind turbine on an XPT will cut rail transport by some ridiculous margin. (watch out for tunnels).