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What Size Furnace Should I Buy?

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The easiest way to find what you need to replace your current furnace is by locating your current unit’s model number. First, locate your data sticker. For furnaces, this is usually located on the inside of the cabinet door, located by removing the top service panel. It can also be found on the inside or outside wall of the cabinet.

Once located, you will see M/N, prod, mod no, or Model Number. Next to this is your model number that you can easily use to search for your new unit.

If you need to know your furnace’s BTU/hr, this is listed next to the labels input/output. You can use this number to calculate your efficiency by dividing your furnace input by furnace output.

For example, when looking at the graphic, Our input is 70,000 BTU/hr and output is 57,000, making the furnace efficiency 81%.

If you’re looking for a general idea of how big your furnace should be you can also use the table below. Note this is just a guideline and there are other factors to consider when choosing HVAC equipment.

Square FootageFurnace BTU
1,000-1,200 sq. ft. Home40,000 - 60,000 BTU
1,200-1,500 sq. ft. Home60,000 BTU
1,500-1,800 sq. ft. Home60,000 - 80,000 BTU
1,800-2,500 sq. ft. Home80,000 - 100,000 BTU
2,500-3,500 sq. ft. Home100,000 to 120,000 BTU

NOTE: Please consult with a local professional to confirm your homes required capacity before placing an order.

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