Gas furnaces use gas to heat your home. In order to find the perfect furnace for your space, you will first need to calculate the square footage of your home in order to estimate how many BTUs the furnace will need to possess, whether you want standard or high efficiency, and what orientation the furnace will need to be.
Here is how to find the proper tonnage for your gas furnace:
Warmest climates: 30-35 BTUs per square foot
Warm climates: 35-40 BTUs per square foot
Mild climates: 40-45 BTUs per square foot
Cold climates: 45-50 BTUs per square foot
Coldest climates: 50-60 BTUs per square foot
You have chosen a 120,000 BTU gas furnace system.
You’ll need to decide which orientation you’d like to choose for your gas furnace. We offer downflow horizontal or upflow horizontal models. Upflow furnaces are often installed in the basement or in the closet, where the ductwork is located above the level of installation. Contrarily, downflow systems are installed in crawl spaces or in areas where the ductwork is below the level of installation.
You also have the option to choose between a “standard efficiency” gas furnace system or a “high efficiency” gas furnace system. On our site, “standard efficiency” stands for gas furnace systems that are 80% efficient and “high efficiency” gas furnace systems are those that are 92% efficiency or higher.
If you would like to add a cooling element to your gas furnace system, you can invest in one of our bundles that include either an air conditioner or heat pump.
To find the desired tonnage for your air conditioner, you’ll first need to calculate the square footage of the space that you’re trying to cool. Typically, the average home requires one ton of air conditioning per 400 to 1,000 square feet. There is a lot of variation in this number since you’ll also need to factor in how many windows the space has and how tall the ceilings are, as these things dictate how easily air flows through your space.
After you have discovered what tonnage will work best for your space, you will then move on to figure out what SEER, or Seasonal Energy Efficiency Ratio, you want your new unit to possess. Essentially, the SEER rating measures the air conditioner's efficiency, which is calculated using the cooling output for a typical cooling season divided by the total electric energy input during the same time frame. Similar to the miles per gallon for a car, an air conditioner's SEER rating is the maximum efficiency rating for the unit. So, the higher the SEER rating, the more efficient the air conditioner will be, likely resulting in lower utility bills and other added benefits. However, it is also important to note that the efficiency of your air conditioning system can also depend on the size of the space you're attempting to cool, your current ductwork, and other variables.
Though it is best to speak to a qualified HVAC technician when on the hunt for a heat pump, we can give you a rough estimate of the tonnage that you will need to cool or heat your space, keeping in mind that any space that is 1,000 square feet or less can simply benefit from a 1.5-ton heat pump:
1,000-1,250 square feet: 2 Tons
1,250-1,500 square feet: 2.5 Tons
1,500-1,750 square feet: 3 Tons
1,750-2,000 square feet: 3.5 Tons
2,000-2,500 square feet: 4 Tons
2,500-3,000 square feet: 5 Tons
Disclaimer: Before making a purchase, you should always check first with your qualified installer to figure out what unit is best for your home or space.