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What size furnace is best?


Published: December 18, 2014

What size furnace do I need?



Most homes end up with oversized furnaces. Some contractors are likely to suggest an oversized furnace due to fear of customer complaint during extreme weather. So, how can you determine what size of furnace you really need? You can do so by determining the BTU and energy efficiency ratings that best match the size of your home.

BTU, or British Thermal Unit, measures the amount of heat requires to raise the temperature of one pound of water by one degree Fahrenheit. For your HVAC system, it measures the number of BTUs that the furnace uses per hour to achieve the same temperature increase. This measurement is the industry standard used to measure the heating efficiency of furnaces, and can help you to estimate how much energy will be required to heat your home.

Here are a few examples of home heating requirements for homes built after 2000:

2,000 square foot home 61,000 BTU
2,500 square foot home 71,000 BTU
3,400 square foot home 88,500 BTU


When selecting a furnace, you’ll want to consider both the BTU and the efficiency rating. If you home requires 71,000 BTU, then you would choose the furnace that comes closest to that number when the BTU is multiplied by the efficiency rating. A Carrier Performance Series 80,000 BTU Single-Stage furnace at 96% AFUE would end up with about 76,800 BTU, which would be sufficient for a home of that size. If you decide to install a Two-Stage unit, you can upgrade to 100,000 BTU because it would spend most of its running time in the low stage. If you choose the basic, single-stage 80% AFUE furnace, then the Carrier Comfort Series 90,000 BTU 80% AFUE furnace would be a good choice.

Since your HVAC system is such a large investment, it’s important to choose the right fit for your home. Do you have additional questions about selecting the right furnace size? Feel free to contact us at (815) 485-6525 for more information and advice.

RCM Heating and Cooling is located in New Lenox, Illinois.


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Tags: BTU, Energy Efficiency, Furnace, Furnace Size, HVAC System, New Lenox, RCM Heating and Cooling