"Coals vary in quality, but on average, a ton of coal contains about as much
potential heat as 146 gallons of heating oil or 20,000 cubic feet of natural
gas, according to the Energy Information Administration. A ton of
anthracite, a particularly high grade of coal, can cost as little as $120
near mines in Pennsylvania. The equivalent amount of heating oil would cost
roughly $380, based on the most recent prices in the state - and over $470
using prices from December 2007. An equivalent amount of natural gas would
cost about $480 at current prices. "

http://www.nytimes.com/2008/12/27/bu...pagewanted=all