A heating device has a combustion chamber and a gas flue configured to guide hot exhaust gas generated in the combustion chamber, the flue having an inlet region and an outlet region and is configured connected to the combustion chamber via the inlet region. Heat transfer ribs having a wall thickness are arranged spaced from each other in the gas flue for the heat transfer from hot exhaust gas to the gas flue. The wall thickness of the heat transfer ribs and/or the distances of the heat transfer ribs to one another are optionally configured to be larger on the sides of the inlet region than on the sides of the outlet region.