Why Is Furnace Sizing So Important?

image of tape measure depicting furnace size and hvac installation

Large furnaces can be impressive but aren’t always the best choice. When highly powerful heating equipment is installed in unsuitable spaces, it provides less-than-standard results. Therefore, focusing on matching your home’s needs instead of going for the largest available size is a must. Selecting a furnace can be complicated because it requires several considerations. Have an experienced HVAC technician assist you in conducting scientific analysis and receive guaranteed compatibility. Keep reading to learn why furnace sizing is crucial.

Explore Our Home Heating Services Call To Schedule A Free, In-Home Estimate

Why Is Furnace Sizing So Important?

Many people choose furnaces based on questionable criteria. As a result, they often get it wrong. Proper guidance ensures that homeowners don’t overshoot or undershoot the mark. On the other hand, inexperience can cause them to suffer adverse effects. Remember that the effects will be worse the farther their chosen furnace is from the ideal size. This situation physically and financially burdens your family. The smallest gaps can still cause irritation, so getting it right from the start is crucial. This will help you have stress-free ownership of your furnace. This article includes some disadvantages you may encounter when the furnace size is incorrect. It also includes valuable information on how to choose the right furnace size that best fits your home.

Related Article: 5 Most Common Thermostat Problems Impacting Your Comfort

Click Here To Call Today: (610) 377-1098

What’s Wrong with Oversized or Undersized Furnaces?

Here are several factors that can be affected when you have an undersized or oversized furnace:

Related Article: Reducing Your Carbon Emissions Through High-Efficiency Heating Systems


image of a homeowner feeling chilly due to undersized home heating system

An undersized furnace won’t have sufficient power to warm your home. This is especially noticeable during winter. The furnace can run on full blast, but you still need to wear layers of clothes and use several blankets. The furnace can work the entire day but still not achieve the preferred temperature.

Having an oversized furnace also creates its own issue. It will warm up some rooms too quickly, making the thermostat think that the set temperature has been reached. This triggers the furnace to shut off even though other areas are still relatively cold. You may hear family members complaining about uneven temperatures.

Call R.F. Ohl Today: (610) 377-1098

Furnace Efficiency

Fluctuations in furnace energy usage depend on its activity level. Furnaces consume more energy during start-up and shut-down. Therefore, these phases should be minimized. Furnaces reach optimum efficiency during their steady state or the phase between the start-up and shut-down phases. 

As mentioned earlier, oversized furnaces are likely to switch on and off quickly. This problem is referred to as short cycling. It occurs constantly throughout the day, using more energy than a right-sized heating system. It never runs steadily. Undersized units tend to overwork to heat your home, causing extreme wear and tear. Heating systems account for most of the energy needs of US households. Inaccurate sizing only causes problems for families and the environment.

Related Article: Top Signs Your Furnace Is Overheating

Energy Costs

image of  a couple calculating bills and home heating

Consuming more energy means you have to pay higher energy bills each month. This is true regardless of whether your heating system is powered by heating oil, natural gas, and propane. An excessively large or small furnace will make you pay more for fuel than necessary. This can mean spending thousands of dollars more each year. You will experience uneven heating around your home instead of comfort. Prevent spending more than you really should, and ensure the furnace is sized accurately. Consult an HVAC professional to compute the right furnace size during a replacement.

Read Our Reviews Click To Schedule An Appointment Now!

HVAC Lifespan

Short cycling doesn’t just affect comfort and efficiency. It also hurts the furnace’s lifespan and its components. A unit that turns on and off in rapid succession will wear out its components faster than expected. You can typically squeeze over two decades of service from the furnace. With an oversized furnace, you may only get a decade or less. This can also occur when you have undersized furnaces.

You may have to shop for a furnace replacement sooner than the expected lifespan and spend thousands of dollars on a new installation. This is a significant cost, so you should spend your money wisely. Have a professional to accurately assess your needs so you can make an informed decision. Experienced HVAC contractors will assist you in finding the right furnace for your home.

Related Article: My Furnace Turns On But No Heat – Why?

How Proper Furnace Size Is Calculated

Here are three ways the furnace size can be properly measured:

Related Article: Fireplace Vs. Furnace: Which Is More Efficient?

1. Load Calculation

Each house has its heating needs. Several factors affect the load, including insulation level, orientation, layout, window type, siding material, and floor area. Conducting a manual load calculation can be complex and lengthy, so professionals usually use advanced software. They will input the values to get immediate results.

Old-fashioned HVAC technicians may depend on simple rules to determine the load, but this usually causes inaccurate assessments. Ensure that you hire HVAC experts who utilize modern techniques to get the exact numbers you can trust. Do this the next time you need to replace your heating system with a new one.

Related Article: What Does AFUE Rating Really Mean?

2. British Thermal Units (BTUs)

If you are unsure about getting a furnace replacement and want to study your options before calling for professional help, you can get a quick estimate using two variables. These are your home’s square footage and the heating factor in your region. You can get a rough estimate when you multiply these two variables.

Outdoor temperatures directly affect indoor heating. For example, you will likely experience high temperatures throughout most of the year if your home is close to the equator. The places get colder as you move up in latitude, causing heating systems to have heavier loads. This is exemplified by California having a heating factor of 30 to 35 BTUs and Minnesota having 50 to 60 BTUs.

Learn More About Our Heating System Services Call To Schedule A Free Estimate

3. Insulation

You can’t control the climate in your region, but you can insulate your home. A highly insulated home means that external factors have a reduced influence on indoor temperatures. Place the insulation across areas susceptible to outdoor influences, such as exterior walls, floors, ceilings, attics, crawl spaces, and the basement. You may also want to seal the gaps along your doors and windows. Good insulation means you can get a furnace size lower than the expected load, and it’ll work fine. For instance, an 800-square-foot home in Minnesota typically requires a 45,000-BTU furnace. However, this load can be significantly reduced when your home has a high level of insulation.

Get Started - Call R.F. Ohl Today


Compatibility is what it’s all about, so go for a furnace size that best fits your home. Don’t aim for the biggest unit you can get your hands on. Ask an experienced HVAC technician to do advanced load calculations for accurate results. Your diligence will surely be rewarded with benefits such as a comfortable home, efficient energy use, considerable energy savings, and an extended system lifespan.

Related Article: What Is The Difference Between A Boiler And A Furnace?

Contact R.F. Ohl For All Your HVAC Requirements

RF Ohl logo

R.F. Ohl provides high-quality HVAC services in Northeastern Pennsylvania, including the Poconos and the Greater Lehigh Valley Region. Our professionally certified technicians are experts in conducting superior heating and cooling services, including boiler tune-ups, air conditioner repairs, furnace installations, and more. You can trust our qualified techs to use their experience and knowledge to service your HVAC system the way it ought to be.

Our company guarantees quality and highly affordable HVAC services in the region. Our maintenance services can improve your home’s comfort and energy efficiency while lowering your heating expenses. We can suggest the best solutions within your budget if you require an HVAC repair or replacement system. Rest assured, all our work is guaranteed. Give R.F. Ohl a call to book a service appointment and get a free, in-home estimate. Call now!

Call Now: (610) 377-1098 Explore Our Case Studies

Click here to contact us today or give us a call at (610) 377-1098 if you have any questions. Click the link to view our service area.