It has been our experience that a finished masonry heater with Temp-Cast standard core kit will cost approximately $2000 to $2500 more than similarly-sized traditional masonry fireplace with a custom glass door. (The cost of a complete Temp-Cast core kit, not including chimney and facing, will generally fall in the range of $4000 to $5000 - contact us for current prices and shipping costs for Temp-Cast core kits.)
The Temp-Cast core kit will typically be only a portion of the final cost of the completed masonry heater, often 50% or less, depending on the size and complexity of the heater design.
A masonry heater with a Temp-Cast core kit is similar in construction to a traditional center-plan masonry fireplace - think of it as a masonry fireplace with an advanced combustion & heating system. They both require a footing, foundation, floor slab, hearth, chimney system and masonry facing, and these elements must be included in your budget for either a masonry heater or an open fireplace. In addition, your Temp-Cast masonry heater will have extra internal components - the Temp-Cast refractory core kit.