Annual fuel utilization efficiency
Encyclopedia
The annual fuel utilization efficiency (AFUE; pronounced 'A'-'Few' or 'A'-'F'-'U'-'E') is a thermal efficiency
measure of combustion equipment like furnace
s, boiler
s, and water heaters. The AFUE differs from the true 'thermal efficiency' in that it is not a steady-state, peak measure of conversion efficiency, but instead attempts to represent the actual, season-long, average efficiency of that piece of equipment, including the operating transients.
The method for determining the AFUE for residential furnaces is the subject of ASHRAE Standard 103. A furnace with a thermal efficiency (ηth) of 78% may yield an AFUE of only 64% or so, for example, under the Standard's test conditions. When estimating annual or seasonal energy used by combustion devices, the AFUE is the better efficiency measure to use in the calculations. But for an instantaneous fuel consumption rate, the thermal efficiency may be better.
Thermal efficiency
In thermodynamics, the thermal efficiency is a dimensionless performance measure of a device that uses thermal energy, such as an internal combustion engine, a boiler, a furnace, or a refrigerator for example.-Overview:...
measure of combustion equipment like furnace
Furnace
A furnace is a device used for heating. The name derives from Latin fornax, oven.In American English and Canadian English, the term furnace on its own is generally used to describe household heating systems based on a central furnace , and sometimes as a synonym for kiln, a device used in the...
s, boiler
Boiler
A boiler is a closed vessel in which water or other fluid is heated. The heated or vaporized fluid exits the boiler for use in various processes or heating applications.-Materials:...
s, and water heaters. The AFUE differs from the true 'thermal efficiency' in that it is not a steady-state, peak measure of conversion efficiency, but instead attempts to represent the actual, season-long, average efficiency of that piece of equipment, including the operating transients.
The method for determining the AFUE for residential furnaces is the subject of ASHRAE Standard 103. A furnace with a thermal efficiency (ηth) of 78% may yield an AFUE of only 64% or so, for example, under the Standard's test conditions. When estimating annual or seasonal energy used by combustion devices, the AFUE is the better efficiency measure to use in the calculations. But for an instantaneous fuel consumption rate, the thermal efficiency may be better.
| Fuel | Furnace/boiler | AFUE |
|---|---|---|
| Heating oil Heating oil Heating oil, or oil heat, is a low viscosity, flammable liquid petroleum product used as a fuel for furnaces or boilers in buildings. Home heating oil is often abbreviated as HHO... |
Cast iron (pre-1970) | 60% |
| Retention head burner | 70-78% | |
| Mid efficiency | 83-89% | |
| Electric heating Electric heating Electric heating is any process in which electrical energy is converted to heat. Common applications include space heating, cooking, water heating and industrial processes. An electric heater is an electrical appliance that converts electrical energy into heat... |
Central or baseboard | 100% |
| Geothermal heat pump | see COP | |
| Air-source heat pump | see HSPF HSPF HSPF is a term used in the heating and cooling industry. HSPF is specifically used to measure the efficiency of air source heat pumps.... |
|
| Natural gas Natural gas Natural gas is a naturally occurring gas mixture consisting primarily of methane, typically with 0–20% higher hydrocarbons . It is found associated with other hydrocarbon fuel, in coal beds, as methane clathrates, and is an important fuel source and a major feedstock for fertilizers.Most natural... |
Conventional | 55-65% |
| Mid-efficiency | 78-84% | |
| Condensing | 90-97% | |
| Propane Propane Propane is a three-carbon alkane with the molecular formula , normally a gas, but compressible to a transportable liquid. A by-product of natural gas processing and petroleum refining, it is commonly used as a fuel for engines, oxy-gas torches, barbecues, portable stoves, and residential central... |
Conventional | 55-65% |
| Mid-efficiency | 79-85% | |
| Condensing | 88-95% | |
| Firewood Firewood Firewood is any wood-like material that is gathered and used for fuel. Generally, firewood is not highly processed and is in some sort of recognizable log or branch form.... |
Conventional | 45-55% |
| Advanced | 55-65% | |
| State-of-the-Art | 75-90% |
See also
- Coefficient of performance (COP)
- Energy efficiency ratio (EER)
- Seasonal energy efficiency ratioSeasonal energy efficiency ratioThe efficiency of air conditioners is often rated by the Seasonal Energy Efficiency Ratio which is defined by the Air Conditioning, Heating and Refrigeration Institute in its standard ARI 210/240, Performance Rating of Unitary Air-Conditioning and Air-Source Heat Pump Equipment.The SEER rating of...
(SEER) - ASHRAE