Tim W wibbled on Tuesday 01 December 2009 16:25
Follow up:
I would say that anthracite (large nut - golf ball to tennis ball sized lumps) is a *very* suitable fuel for these little heaters.
For the record, so far, running semi flat out for 12 hours and slumbering overnight, it's taking about 10kg coal a day (£3.30).
Electric heating load reduced from 4kW all day to typically 1kW fan heater round the back.