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The plain-English glossary.
BTU, ULSHO, AFUE, heat pump vs. furnace — what these terms actually mean for your home, from a family business that's been explaining them since 1980.
Heating Fuels
BTU (British Thermal Unit)
The basic unit of heat — the energy needed to raise one pound of water by 1°F.
ReadUltra-Low-Sulfur Heating Oil (ULSHO)
Modern heating oil refined to contain 15 ppm sulfur or less — cleaner, more efficient, and easier on equipment.
ReadBioheat® Fuel
Ultra-low-sulfur heating oil blended with renewable biodiesel made from soybeans, recycled cooking oil, or other sources.
ReadPropane (LPG)
A clean-burning liquefied petroleum gas used for heating, cooking, hot water, generators, and more.
ReadDegree Day
A measure of how cold a day was relative to 65°F — the foundation of automatic fuel delivery.
ReadTank Monitor
A small wireless device on your fuel tank that reports the level back to your dealer in real time.
ReadEquipment
Furnace
A heating system that warms air and distributes it through ductwork.
ReadBoiler
A heating system that heats water and circulates it through radiators, baseboards, or radiant tubing.
ReadHeat Pump
An electric system that moves heat instead of generating it — providing both heating and cooling from one unit.
ReadMini-Split (Ductless)
A heat pump that delivers conditioned air directly to a room with no ductwork.
ReadHeat Exchanger
The metal core inside a furnace or boiler where combustion heat is transferred to your air or water.
ReadAFUE (Annual Fuel Utilization Efficiency)
The percentage of a heating system's fuel energy that becomes useful heat over a typical year.
ReadSEER2
The current efficiency rating for air conditioners and heat pumps in cooling mode — higher is better.
ReadStill have a heating or cooling question?
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