I have never heard of anyone burning bit in an Axeman or an AHS, so perhaps there are a group of Bunny Huggers next door that think Anthracite will be the next Chernobyl.
They are heating something substantial, and it is possible that NG is available, and the city requires you to tie in. 500K is not that big a unit, but more than most happy homeowners see.
6 AA 260's lined up makes more of a statement, with a 100 ton coal bin......
In Keene, NH, a few applications with a pair of 260's running making steam...over 40 years now.