Recess required, see size requirments, The engine fits a standard opening, 16" wide x 22" high, & most importantly only requires a 5" (128mm) fireplace depth, making it perfect for the modern pre-cast chimney/flue system, All fires a primarily designed to provide top up heat & are not intended as a primary heat source, All fires must be installed in accordance with the manufacturers' installation instructions & current building regulations, To calculate running costs, multiply the heat input of the fire by your gas/electricity tariff (heat input x pence per k W/hr = running cost), B&Q Homefit could fit this product for you contact 01236 634557 for further inforamtion