What are BTUs?

What are BTUs?The British thermal unit (BTU) is a term that describes energy and heat production, and it’s also how the HVAC industry describes the capacity of combustion heating systems. When applied to furnaces and boilers, the number of BTUs indicates the amount of fuel the unit uses.

Combustion heating systems by their nature are never 100 percent efficient, although new technology has improved them to the point where some use nearly all their heat output for home heating.

Understanding Furnace Ratings

Besides listing the total BTUs, furnaces and combustion heating systems use, they must also indicate their AFUE (annual fuel utilization efficiency) ratings that indicate how much of the fuel the system uses that translates to home heat.

Expressed as a whole number, they’re actually the percentage of usable heat versus what’s wasted. Waste heat usually goes up the chimney in the form of combustion gases, and the most efficient systems pull the heat from those gases and use it indoors instead of sending it outside.

When HVAC professionals size a furnace for a home, they use a combination of its BTU capacity and the AFUE rating to arrive at the best fit, to avoid under- or oversizing a new system.

A system that puts out 80,000 BTUs of heat but is only 85 percent efficient provides a net capacity of 65,000 BTUs. Conversely, equipment with a capacity of 70,000 BTUs but is 99 percent efficient puts out 69,300 BTUs of usable heat.

Why It Matters

Understanding BTUs helps you interpret your heating bills with your current system and provides a solid basis for choosing your next heating system. Smaller heating systems with greater efficiency do cost more initially, but use less fuel over their lifetimes, which cut energy bills each time they run.

The BTU is the centerpiece of home heating systems regardless of the fuel you use. If you’re in the market for a new system or want to improve the performance of your existing equipment, contact C.R. Wolfe Heating & Air Conditioning, providing HVAC services for Middletown homeowners.

Our goal is to help educate our customers in Middletown, New York about energy and home comfort issues (specific to HVAC systems). For more information about BTUs and other HVAC topics, download our free Home Comfort Guide or call us at 845-367-4482.

Credit/Copyright Attribution: “geralt/Pixabay”

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