Ashful
Minister of Fire
Yes per ton they are similar. But a ton of anthracite takes up allot less space than a ton of bituminous or sub bituminous. So your load of coal in you stove has allot more btus in it with anthracite than with the other two.
This is interesting. As pointed out previously, the energy per unit weight between the two has a lot of overlap, with the anthracite being skewed only slightly higher. Likewise, the weight per volume overlaps to a large degree, both having almost the same upper limit, but some bituminous running much lower:
Anthracite: 50 - 58 lb/cu.ft.
Bituminous: 42 - 57 lb/cu.ft.
So, I guess it would be most correct to say that some bituminous has much lower energy than anthracite, but perhaps not all of it.