All condensing furnaces manufactured after 1992 must have an AFUE rating of at least:

The required annual fuel utilization efficiency (AFUE) rating for condensing furnaces manufactured after 1992 is set at a minimum of 90%. This standard is significant because it reflects the efficiency of these furnaces in converting fuel into usable heat. Condensing furnaces are designed to extract additional heat from exhaust gases, which significantly increases their efficiency compared to older models.

The requirement for a minimum AFUE of 90% signifies a commitment to energy efficiency and environmental standards. By achieving this level of efficiency, condensing furnaces not only reduce energy consumption but also lower greenhouse gas emissions, contributing to a more sustainable approach to heating.

Regarding the other options, while they may indicate various efficiency ratings for different types of furnaces or ages, only the 90% AFUE rating aligns with the regulations specified for condensing furnaces produced after 1992. Understanding these efficiency standards is crucial for anyone involved in the heating industry, as it ensures compliance with energy codes and helps consumers make informed choices about their heating options.