The Aarrow Acorn 5 is the slightly wider cousin to the Acorn 4 stove (only 40mm wider though), giving out 5kW instead of 4kW. A backboiler is available for the Acorn 5 stove which, if fitted, provides 6,840 BTU to the water whilst the stove then gives out 3kW of heat to the room. The Acorn 5 has an airwash system to help keep the glass free of deposits, and is a multifuel stove. When burning wood in the Acorn 5 the lower air vent is closed and the upper air control is used to control the fire. This situation is reversed when burning coal.