What Size Furnace Do I Need? A Pittsburgh Tech Answers

| Posted in:  Help Guides/Heating

The simple answer: there isn’t one (unfortunately). The size of furnace your home needs is based on a number of factors, including:

  • Local climate
  • Layout of your home
  • Insulation levels of your home
  • And much more

The easiest way to accurately determine what size of furnace you need is to speak with an expert who can evaluate all of these factors and how they fit together. Below, we’ll explore some of these factors and discuss:

  1. How furnace size is measured
  2. The importance of getting the right-sized furnace
  3. How to find the right size furnace

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How furnace size is measured

Furnaces are measured in BTUs (British Thermal Units), a measurement of how much heat the furnace can put into your home in 1 hour.

Let’s break that down. One BTU is approximately equal to the energy released by burning one match. Essentially, the higher the BTU output, the more heat a furnace is capable of releasing into a home per hour.

Residential furnaces range from 40,000 to 200,000 BTUs and most homes usually need a furnace between 60,000 and 120,000 BTUs.

A common misconception is that the higher the BTU output is, the better it is. This is not correct! First of all, how many BTUs are actually delivered into your home depends on furnace efficiency, the condition of your ductwork and several other factors.

Example: A 100,000- BTU furnace has an efficiency rating of 80%. This furnace will probably only deliver about 80,000 BTUs of energy per hour (other factors will also influence this).

And secondly, a furnace that’s too big or small can harm your system and reduce your indoor comfort (more on that below).

Importance of getting the right-sized furnace

Bigger is not always better, especially when it comes to installing a furnace. Why?

A furnace that is too large will heat the space fairly quickly and then shut off. This issue, called “short cycling” can cause:

  • High energy bills: starting up a furnace takes more energy than running one. If your furnace is stopping and starting frequently, this will increase your energy bill.
  • Uneven temperatures: Short spurts of heat don’t give warm air enough time to circulate, creating some spaces that are very warm and some that are cold.
  • Shortened furnace lifespan: Constant starts and stops can quickly wear on furnace parts, causing them to expire faster.

On the flipside, a furnace that is too small for your home will run all the time without heating your home properly. This constant running can also increase energy bills and wear your furnace out quickly.

How to find the right size furnace

A load calculation is a complex analysis that will determine what furnace size is ideal for your home.

This calculation takes into account factors such as:

  • Local climate
  • Height of your home’s ceilings
  • Insulation levels of your home
  • Size, layout and orientation of your home
  • Materials your home is made of
  • Size, orientation, age and number of windows in your home
  • Number of people in your home
  • Type of roofing on your house
  • And more

Since this calculation looks at so many factors, it’s better to have a professional handle it than to attempt it yourself. That way, you’ll know you’re getting the right size furnace for your home.

Ready to invest in the right-sized furnace?

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Our experienced techs can accurately evaluate what size of furnace is perfect for your home as well as safely install it.

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