What Size Furnace Do I Need? A New Jersey Tech Answers | Air Experts

As HVAC professionals, we’re used to being asked, “What size furnace do I need?”

We’re also used to hearing a lot of wrong information about how to determine which furnace size is right for your home. Only a licensed professional can answer this question—and they can only provide an accurate answer after they perform a “load calculation.”

Below, we’ll answer two questions to help you find the right size furnace, including:

  1. What is a load calculation?
  2. Why does furnace size matter?

We’ll even throw in an extra tip to make sure you don’t fall into the hands of the wrong technician.

What is a load calculation?

A load calculation is an analysis of your home and heating needs. It helps determine how much heat your home needs and the size furnace that can keep up with that heat load.

During a load calculation, a professional will assess:

  • How many rooms are in your home
  • The layout and orientation of your home
  • The location of your home (warm or cold climate)
  • Number of windows
  • The rate that air leaks out of your home
  • Amount/quality of insulation
  • Whether or not your air ducts are sealed

Sound complicated? It is! That’s why an experienced tech will need to perform this calculation.

Why does furnace size matter?

A furnace that is too big (oversized) or too small (undersized) can cause issues, like:

  • Shortening the lifespan of your unit
  • Increasing your utility bills
  • Resulting in costly repairs
  • Causing temperature discomfort (hot and cold spots)

An oversized furnace: A furnace that is too large for your home will heat quickly, causing the furnace to shut off (and turn back on) frequently. This is called short cycling. This causes excessive wear and tear on your furnace, shortening its lifespan. Additionally, when your furnace shuts on and off frequently, it doesn’t give the warm air time to circulate throughout your home, causing areas that are very warm and areas that are cool.

An undersized furnace: An undersized furnace will have the opposite problem. Because it’s too small for your space, it will run constantly to try and heat your home properly. Unfortunately, an undersized furnace can result in the same issues (temperature discomfort, increased bills, shortened lifespan).

Beware techs who offer rule-of-thumb sizing estimates

As we mentioned above, a technician will need to come to your home and conduct a load calculation to be able to accurately determine which furnace size is right for your home.

Techs who will give an estimate based on your home’s square footage or provide sizing advice over the phone without seeing your home are not the kind of techs you want installing your furnace. This kind of sloppy sizing could result in an oversized or undersized furnace, causing you problems and expensive repairs down the road.

Need a New Jersey pro’s help?

Whether you need an expert to determine which size furnace you need or you’re ready for a furnace installation, our team is here to help. Schedule service today!

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