Furnaces rated at average efficiency tend to experience what percentage of off-cycle losses of the fuel they consume?

Furnaces rated at average efficiency typically experience about 20% off-cycle losses of the fuel they consume. Off-cycle losses occur when the furnace is not actively heating but is still losing heat through the flue, duct systems, or other components. This loss is particularly significant in average efficiency furnaces due to less effective insulation and design.

A 20% off-cycle loss reflects the balance between heat retention during non-operational periods and the inherent inefficiencies in older or less advanced furnace designs. Higher efficiency models are generally designed to minimize these losses with improved insulation and tighter seals, which is why the percentage here is representative of average units rather than high-efficiency models. This understanding is critical for those looking to improve home heating efficiency or considering replacement options for better energy usage.