What is the typical AFUE rating for natural gas natural draft systems?

The typical AFUE (Annual Fuel Utilization Efficiency) rating for natural gas natural draft systems generally falls within the range of 60-70%. This rating provides a measure of how efficiently a heating system converts fuel into usable heat over the course of a year. Natural draft systems rely on the natural convection of flue gases to vent exhaust, which tends to limit their overall efficiency compared to more advanced heating systems, such as those using forced draft or condensing technology.

When examining natural draft systems, it becomes evident that they have inherent design limitations in terms of heat recovery and venting. The 60-70% range reflects a balance between basic operational efficiency and the typical technologies used in such systems, which do not capture and reuse heat from exhaust gases as effectively as higher-efficiency models. Systems with an AFUE above 70% are typically indicative of more modern, efficient designs or technologies, which is why the 60-70% choice aligns most accurately with the characteristics of natural gas natural draft systems.