What is a BTU and what does it mean to you? In winter or summer, the number of BTUs added or removed from the house, respectively, is critical to indoor comfort. It’s also an important element of the calculations utilized for efficiency rating that help you evaluate the most energy-efficient heating and cooling equipment when you’re shopping for an upgrade.

BTU is short for British Thermal Unit. It’s the universally accepted measurement for a unit of heat energy. In winter, BTUs of heat energy are added to the house by your furnace or other heating system to make the premises comfortably warm. In summer, conversely, your air conditioner extracts

BTUs of heat from indoor air and moves them outdoors to keep things cool. When expressed in raw numbers, the amount of BTUs a furnace generates or an air conditioner extracts is referred to as the unit’s “capacity.”

The BTU also figures prominently in both the AFUE (Annual Fuel Utilization Efficiency) furnace rating as well as the central air conditioner’s SEER (Seasonal Energy Efficiency Ratio) rating.

• AFUE calculates the percentage of BTUs of heat energy a furnace generates that actually contribute to heating the home versus the percentage that is normally lost in the combustion process as hot gasses are exhausted up the vent pipe. A standard efficiency furnace typically has an AFUE around 80%. A high efficiency furnace incorporates an extra heat exchanger to harvest this lost heat and therefore delivers AFUE ratings up to 95%.
• For an air conditioner, how many BTUs of heat the unit can remove from your home over a specific time span in ratio to the amount of electricity it will use during that time is important information when evaluating both operating costs and cooling performance. The SEER rating expresses that calculation in a single numeral. A standard efficiency A/C unit today has a SEER rating of 14 while high-efficiency units range as high as 20 or more.

Ask the experts at Powers Heating & Air for more about how the BTU affects indoor comfort and operating costs year-round.

Our goal is to help educate our customers in Peachtree City, Georgia and surrounding areas about energy and home comfort issues (specific to HVAC systems). For more information about other HVAC topics, download our free Home Comfort Guide or call us at 770-487-2040.

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