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AIR CONDITIONING & HEAT PUMP SYSTEMS
BACKDRAFTING HEATING EQUIPMENT
BACKUP HEAT for HEAT PUMPS
BANGING HEATING PIPES RADIATORS
BLOWER FAN OPERATION & TESTING
BOOKSTORE - InspectAPedia
BTU USAGE MONITORS
CARBON MONOXIDE - CO
CIRCULATOR PUMPS & RELAYS
DIAGNOSTIC GUIDES A/C / HEAT PUMP
DIAGNOSE & FIX HEATING PROBLEMS-BOILER
DIAGNOSE & FIX HEATING PROBLEMS-FURNACE
DIRECT VENTS / SIDE WALL VENTS
DRAFT REGULATORS, DAMPERS, BOOSTERS
DUCT SYSTEM & DUCT DEFECTS
ELECTRIC MOTOR DIAGNOSTIC GUIDE
FAN, AIR HANDLER BLOWER UNIT
FLOODED HEATING EQUIPMENT REPAIR
FLUE SIZE SPECIFICATIONS
GAS BURNER Flame & Noise Defects
GAS PIPING, VALVES, CONTROLS
GEOTHERMAL HEATING SYSTEMS
HEAT PUMPS, DIAGNOSIS, REPAIR
HEATING COST SAVINGS METHODS
HEATING OIL PIPING TROUBLES
HEATING OIL TANKS
HEATING SYSTEM NOISES
HEATING SYSTEM TYPES
GAS LP & NATURAL GAS SAFETY HAZARDS
MANUALS & PARTS GUIDES - HVAC
MIXING / ANTI-SCALD VALVES
MOTOR OVERLOAD RESET SWITCH
NOISE, HEATING SYSTEMS
ODORS FROM HEATING SYSTEMS
OIL FILTERS on HEATING EQUIPMENT
OIL FILL PIPE LEAKS
OIL SPILL CLEANUP / PREVENTION
PLASTIC Plexvent / Ultravent RECALL
PUFFBACKS, OIL BURNER
RELIEF VALVE LEAKS
Reset Switch - Heater Primary Control
RESET SWITCH - ELECTRIC MOTOR
Reset Switch - Stack Relays
SAFETY, HEATING INSPECTION
SAFETY RECALLS CHIMNEYS VENTS HEATERS
SOLAR HEATING SYSTEM DESIGNS
SOOT on OIL FIRED HEATING EQUIPMENT
STEAM HEATING SYSTEMS
THERMOSTATS, HEATING / COOLING
VIDEO GUIDES: Heating System Videos
WINTERIZE A BUILDING
WOOD, COAL STOVES & FIREPLACES
WOOD STOVE SAFETY
ZONE VALVES, HEATING
This article gives a definition of AFUE and explains AFUE (Annual Fuel Utilization Efficiency) or heating system efficiency ratings and numbers.
The articles at this website describe the basic components of a home heating system, how to find the rated heating capacity of an heating system by examining various data tags and components, how to recognize common heating system operating or safety defects, and how to save money on home heating costs.
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How is heating boiler efficiency or economy measured? What does boiler AFUE mean?
Here's a very rough example: if the AFUE number for your heater is 80%, that means that for every dollar you spend on heat, twenty cents "goes up the chimney" or is lost in various other ways, and eighty cents of each heating dollar shows up in your occupied space as heat.
Each model of heating boiler or furnace is assigned an AFUE number. Our page top sketch of a high efficiency furnace is provided courtesy of Carson Dunlop Associates.
At left we illustrate a high efficiency gas furnace - expected to have a high AFUE number. Sketch courtesy of Carson Dunlop Associates.
AFUE is an abbreviation for Annual Fuel Utilization Efficiency. In short, the AFUE tells you, for each dollar you spend on energy for heating by gas, oil, or another fuel, just how much of your dollar shows up inside the occupied space of your building as heat. Higher AFUE is better.
If your boiler or furnace or steam boiler has an AFUE rating of 90, that means that for every dollar you spend on fuel, 90 cents worth of heat is delivered into your building. The remaining 10 cents is lost in inefficiency such as heat that escapes up the chimney along with the products of combustion.
What is the Reliability & Accuracy of Heating System Efficiency Ratings - AFUE?
AFUE is not the whole story of heating cost efficiency. A high-efficiency heating system that has not been cleaned and serviced may be running poorly and wasting money.
In fact, an 85% AFUE heating boiler that has not been cleaned might be running at an efficiency much lower, perhaps 65%.
Furthermore, if your building is drafty or poorly insulated, you may be delivering heat at high efficiency but losing it from the building much faster than necessary.
These articles can help with a more complete approach to saving money on heat:
What are the Current AFUE Requirements for Heating Equipment?
Other Heating System Performance Measurements & Standards
Also see our definition of HSPF, SEER, and other measurements found at SEER RATINGS & OTHER DEFINITIONS or select a topic from the More Reading links shown below.
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Frequently Asked Questions (FAQs) about the definition of AFUE or heating system efficiency measurements
Questions & answers or comments about AFUE and heating system efficiency ratings, measurement, and improvement
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