What AFUE describes
Annual fuel utilization efficiency estimates the share of fuel energy converted to useful seasonal heat under test conditions. It does not include all electrical use, distribution losses or the effect of poor installation.
Condensing furnaces
High-efficiency gas furnaces recover additional heat from exhaust and produce condensate. They require suitable vent materials, drainage and freeze protection. A blocked drain or vent can stop the furnace.
The rest of the system
Leaky ducts outside conditioned space, dirty filters, weak insulation and uncontrolled air leakage can erase part of the benefit of efficient equipment. Comfort upgrades often work best as a package.
Compare operating assumptions
Ask estimators to state fuel price, heating load, equipment output and maintenance assumptions. Savings projections without those inputs are difficult to evaluate.
- What changed immediately before the problem?
- Does the issue affect airflow, heat production or both?
- Is there an error code, odour, leak or repeated shutdown?