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Can a Furnace Unit be Oversized?

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Can a Furnace Unit be Oversized?

Posted On: March 18, 2025

Can a Furnace Unit be Oversized?

a furnace can absolutely be oversized, and it’s a more common problem than you might think. While it may sound like having a more powerful furnace is a good thing, an oversized unit can actually cause several problems for your home’s comfort and efficiency.


Signs Your Furnace Might Be Oversized

  1. Short Cycling — The furnace turns on and off frequently because it heats the space too quickly, shutting off before completing a full heating cycle. This leads to uneven temperatures and increased wear on the unit.


  2. Uneven Heating — Some rooms may feel too warm, while others stay cold because the heat doesn’t distribute evenly before the system shuts off.


  3. High Energy Bills — Short cycling uses more energy since the furnace draws the most power during startup. Constantly restarting increases your energy costs.


  4. Excessive Wear and Tear — The repeated on/off cycling causes parts to wear out faster, leading to more frequent repairs and a shorter lifespan for the unit.


  5. Poor Humidity Control — Furnaces also help control humidity levels in your home. An oversized unit doesn’t run long enough to properly remove moisture from the air, leaving you with a clammy, uncomfortable environment.



What Causes an Oversized Furnace Installation?

  • Improper Load Calculation — If the HVAC contractor didn’t properly calculate your home’s heating load (taking into account square footage, insulation, windows, etc.), they may have installed a larger furnace than necessary.
  • "Bigger is Better" Mentality — Some people assume a larger furnace will heat the home faster, but this actually leads to inefficiency and discomfort.
  • Old House Upgrades — If you’ve added insulation, replaced windows, or improved energy efficiency, your original furnace may now be oversized for your current needs.

How to Fix an Oversized Furnace

  • Replacement — The most effective fix is replacing the unit with one properly sized for your home. An HVAC professional can perform a Manual J Load Calculation to determine the right size.
  • Adjustments — In some cases, technicians can modify the blower speed or adjust gas pressure to reduce output, but this is more of a temporary fix.
  • Zoning Systems — If replacement isn’t an option, installing a zoning system can help direct heat to specific areas more effectively.


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See What Our Customers Are Saying:

by Colin Vernon on Twintech Heating and Cooling

They've cleaned my furnace a couple of times and mentioned that the hot water tank standards were going to change soon so I decided to change mine out.

There were a few challenges during the process but the installers handled the problems without missing a stride! I now have really hot water again!

by Heidi B on Twintech Heating and Cooling

Highly recommend Twintech Heating company, we got honest and detailed information on what was needed to replace and install a new gas furnace. Bob and Greg made us feel comfortable withe process through their thorough explanation and knowledge of the right furnace for our needs. The professionalism and courteous friendly attitude towards the customer is what we liked the most as they treated us like family. So happy with our decision and new furnace we will be looking into get our rental water heater replaced and installed by Twintech team. We feel better having their knowledge on our side and will only trust them with any further maintenance of furnace.

by Kirushanth Rasiah on Twintech Heating and Cooling

Customer service and knowledge is priority in this industry, and Twintech has it. I've dealt with their team for maintenance and a furnace replacement. They're accommodating and make great recommendations, and came through at a great price over the big guys in the industry. They'll be my next call when I need service or maintenance.

by Leonard Glass on Twintech Heating and Cooling

I decided that the noises and age of the existing furnace which was old and not very efficient to replace it. Gave Greg a call and Grant and Greg got to work on it. Because of supply issues with the current heating type that would be an easier install Greg convinced me to change the location of the system and it would provide me better service for heat and efficiency. I had skeptical but went ahead anyway putting trust in Greg And Grant. Greg, Grant and Mitch came through and in 2 days had completely relocated my heating and A/C system. I can honestly say Greg was right my old house has been warmer and more evenly heated as it ever was. For anyone reading this rather long winded review can take my word for it, Twin Tech can take care of your needs.

by Nicole Alain on Twintech Heating and Cooling

I called Twin Tech when my air conditioning stopped working. Greg came over to diagnose the issue - the same day. He was able to diagnose the issue and resolve it quite quickly. Although it was a quick fix, Greg was very thorough in explaining the issue and provided great advice. Not to mention, I felt very comfortable having Greg in my home - which I consider very important when hiring a service provider. Twin Tech will be my go-to from now on. Thank you!!

by Cibele Ceroni on Twintech Heating and Cooling

Great Team! Furnace broke in the weekend, Bob visited same day and Greg installed new one on Monday. Team was professional, respectful and knowledgeable. Installation went very well, Greg found solutions to challenges, like hiding new conduits in the ceiling. Looks nice and new furnace is working great. Five Stars.

by Jackie Graham on Twintech Heating and Cooling

I used Twintech to install a new furnace for my home. Bob was terrific in explaining the sizing options and why the 2 stage furnace was the best option for me. Greg did a great job installing, clean and on time. Finished work looks great but the best part is how it works. The 2 stage heating is so much more comfortable. I run the fan continuously to keep the indoor air clean. Great investment! Would highly recommendTwintech!

by Anthony Silva on Twintech Heating and Cooling

I’m going to start this by saying I’m a very particular customer. My background is in mathematics and mechanical engineering so I have an eye for detail and a respect for technical knowledge.
Greg had already done an AC inspection and replaced a water heater tank and there was no question in my mind who to deal with replacing my rickety old furnace after it got pooched.
Bob dropped in ahead of time and clearly (and knowledgeably) outlined all technical, price and operational options.
Greg showed up on time, on the agreed date and did a fantastic job. (The OLD furnace was a house of horrors and was installed in a keystone cops sort of way- careless.)
The work Greg did was HIGHLY PROFESSIONAL and FAR MORE FUNCTIONAL than what I had.
I’m also a musician with many instruments so maintaining predictable humidity/temperature is extremely important to me. Greg recognized this as did Bob. You NEVER feel like you’re being brushed off.
In summary, if you’re looking for PROFESSIONAL, QUALITY results by an EXPERIENCED, THOUGHTFUL team
(that also happen to be FRIENDLY and ATTENTIVE ) then you’ve come to the right page!!

by Karen Morgan on Twintech Heating and Cooling

Once again Twin Tech came through and fixed my furnace. A young man by the name of Mitch came by tonight and he was so nice explained everything he was quick he was clean he turned off the lights even when he left the furnace room it’s just above and beyond Twin Tech always delivers and I just found out about them last year and I will use no one else but thanks again Mitch you are fantastic

by Richard Liu on Twintech Heating and Cooling

I had a problem with the Furnace (Armstrong ultra V) and Greg diagnosed it on the phone. Even told me what the issue was and I was able to fix it. This level of service from a Business that is almost unknown today.

If you require service, reach out to Greg. I will definitely use them in the future!

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See What Our Customers Are Saying:

by Robert Rogers on Twintech Heating and Cooling

Very pleased with the professional service that TwinTech Heating and Cooling provided in replacing my furnace. I got several quotes from different service providers. Their price was excellent and they explained the features very well. We are very glad we went with TwinTech and highly recommend their services.

by Robert Mizuno on Twintech Heating and Cooling

We were new homeowners in need of a second opinion. TwinTech Heating & Cooling were Amazing and professional. Very knowledgeable and great service all around. Recommend to anyone looking for honest and reliable services. Treated with respect and care. Thank you Greg, Mitch and Bob!

by Ruth on Twintech Heating and Cooling

TwinTech is an excellent and honest company! I called them for a second opinion after being told by another company that I needed to replace my furnace. Turns out this was not the case at all! I did not need a new furnace. TwinTech did not push to make an unnecessary sale and saved me from a huge expense. Bob and Mitch were extremely professional and above all honest! I definitely recommend TwinTech!

by Anna Chin on Twintech Heating and Cooling

Amazing experience with TwinTech Heating & Cooling! Their team was professional, knowledgeable, and efficient from start to finish. They installed my new furnace quickly and left everything spotless. The technicians took the time to explain everything and made sure I was comfortable with the system before they left. Great customer service and fair pricing. I highly recommend them for anyone needing HVAC services!

by Connor Agnew on Twintech Heating and Cooling

Great experience all around. Bob was sharp and easy to talk to, and Greg handled the installation perfectly. Would hire them again in a heartbeat.

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