Switched over from wood to coal this year and have it adjusted nice. Burning "Stove" size anthracite coal. I did improvise a firebox reducer because a full firebox is just too much. i needs to open draft occasionally and "work " a little to keep a nice fire going. I've effectively halved the firebox with plate steel and refractory brick. I build a nice deep coal fire in the front. I have about 3500 sq ft of living space to heat with the "dump" zone in my garage. I get am getting a good 12 hour burn cycle when it is in the 20's outside. No kidding..... Love this stove... Just ordered another 5 tons of anthracite.