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Monday, October 07, 2013

Fuel economy is high on most decision-making lists for those who are buying a car. The same should be true for homeowners considering a new furnace, particularly here in northwest Indiana and southwest Michigan, where lake-effect winters can make for long heating seasons. Happily, a ratings system has been implemented which makes appliance efficiency as easy to evaluate as automotive miles-per-gallon figures. It's called the AFUE.

Spelling Out AFUE

AFUE stand for Annual Fuel Utilization Efficiency. It describes a home heating appliance's fuel use, making comparing like-for-like equipment a cinch. Used alongside the unit's thermal efficiency value, it's an indispensable decision-making tool.

Explaining AFUE

The more familiar 'thermal efficiency' figure expresses a unit's effectiveness when operating at its peak. The AFUE value doesn't assume any heater can achieve that level of performance in real life, because it won't be working at the steady rate estimated by thermal efficiency measurements. Instead, AFUE predicts the performance you can expect in an average, real-usage season.

Determining AFUE

Furnaces and water heaters burn fuel to create heat. Whether it's electricity, propane or natural gas, the fuel contains a calibrated amount of energy when it's delivered. That energy is measured in British thermal units, or BTUs. The heater converts incoming BTUs in the fuel to usable, outgoing BTUs that you experience as heated air or water. Efficiency is simply a comparison between the BTUs going in, and the BTUs coming out. The difference is waste, primarily warm exhaust gas. By expressing energy coming out as a percentage of energy going in, AFUE gives the potential purchaser an easy-to-understand measurement of that efficiency.

Evaluating AFUE Values

The higher the AFUE percentage, the more efficient the appliance. It's really that simple. The percentage is expressed numerically, and the higher that number, the greater its efficiency in converting incoming BTUs to outgoing BTUs. That translates directly into more heat for every fuel dollar.

The specialists at are experts on all aspects of heating efficiency, including AFUE values. Schedule a free consultation through our 'Find A Contractor' page, and turn a little time into big savings.

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