How To Size A Furnace For My House

An important question any homeowner should ask themselves is how big should my furnace be? Having the proper size furnace ensures proper heating throughout your home. Furnaces too small will mean insufficient heating while furnaces too big will mean excessive energy consumption.

Both of these scenarios equals more costs, less heating, and faulty operations from your home’s furnace. It is important to get the sizing right, have an HVAC technician come in for a consultation so that your home is set for the next 10-15 years.

Here is a more detailed look on improper furnace sizing.

HVAC System Sizing

What are the steps to properly sizing your potential furnace?

  1. Calculate the square footage of your home. Before you start, it is important to mention that you do not have to measure for rooms that do not have vents, and you do not have to measure for rooms that you are not expecting to heat.  To get the total square footage for your house start by measuring the length and width of each room, take these two measurements and multiply them together. Take all the numbers you have collected and add them together to get the total square footage.
  2. Take climate into account. For example, homes that experience colder winters like in the Midwest will require a furnace with more heating power.
  3. British Thermal Units. Gas furnaces are measured in British thermal units or BTUs. A BTU is the amount of water energy needed to cool or heat one pound of water by one degree Fahrenheit.
  4. Figuring out a rough estimate. We cannot stress the importance of taking into account your climate when determining your furnace size; you will need an accurate software to help you factor that part of the equation in.
  5. Consult an HVAC Technician for Accuracy. Other factors need to be accounted for like the age, construction of your home, the amount of insulation, climate, and the seals you have to provide the necessary information to perfect sizing for your furnace. A licensed HVAC technician with the proper experience, and technology can help you figure out all the missing components to your equation.

For rough estimates, it is recommended that you allow 20-40BTUs per square feet for furnaces in California. Example: 2,000 square footage x 30 or 45BTU = 60,000 – 90,000 BTU rough estimate for furnace size

New furnaces are expensive pieces of equipment, but they are necessary to ensure the comfort of your home, especially during the cold winter months.

If you are going to spend the money on getting a new furnace, it means you are making a 10-15 year investment for your home. You do not want to constantly pay for repairs on a furnace that looked like the right fit, but wasn’t.

Beware of an Oversized Furnace

An oversized furnace can lead to a whole list of issues for your home, including:

  • Unequal distribution of heat
  • Uncomfortable distribution of heat
  • Confusing temperatures cause furnace to cycle on and off
  • Reduction of your furnace’s lifecycle
  • Failing heat exchangers

These are all problems and telltale signs that your furnace may be too big for your home. If your furnace breaks down from constantly cycling on and off, you will need to spend more money replacing it with a new one.

Beware of an Undersized Furnace

The problem with an undersized furnace is the times that they do not work well, and this will mean your rooms being unable to reach the desired temperature.

When your furnace is failing to reach the desired temperature, it will constantly run in an attempt to, this will lead to your furnace overworking itself and causing higher costs for energy. There will be times where you will find your furnace is on and working, but your home is still cold due to insufficient heating.

Rewards of a Perfectly Sized Furnace

The benefits of having a correctly sized furnace are simply the fact of it working the way you would expect it to. The right furnace for the right home means warm temperatures when you need it with a tiny margin of error (maybe 1%).

Contact One Hour Heating & Air Conditioning® of the Bay Area to handle all your furnace needs from sizing, maintenance and repairs.