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The Importance of a Properly Sized HVAC System: Finding the Goldilocks Zone

By Aztil –

Proper sizing is the most important part of any new HVAC installation. Whether you’re replacing your air conditioner, furnace, or heat pump, you must ensure it has the right capacity for its intended service area. This is key to avoiding hot and cold spots and abnormally high energy bills. Oversized and undersized appliances can’t work efficiently. They also experience countless performance problems, including short cycling, icing, overheating, and diminished humidity control. The first step when selecting a new HVAC system is to schedule a professional consultation. Our technicians can assess your home and household to find a properly sized HVAC system.

The Goldilocks Zone: Getting HVAC Sizing “Just Right”

The Goldilocks Principle states that if HVAC systems are not sized correctly, they can be too hot or cold. In the Goldilocks zone, the sizing for HVAC systems is “just right” and homeowners can expect even and consistent performance throughout their service lives.

Oversized Systems: What Happens When HVAC Equipment Is Too Large

HVAC sizing denotes the heating or cooling capacity of heaters, heat pumps, and air conditioners. If you choose a model that’s too large for your home, it will run short and intense heating and cooling cycles that use a lot of energy and cause accelerated HVAC wear. This is called short cycling, and with these short blasts of heated or cooled air, your living space will never be truly comfortable. Installing overly large units can also result in the frequent need for costly HVAC repairs and shorter equipment lifespans.

Undersized Systems: The Drawbacks of Installing Units That Are Too Small

Undersized HVAC equipment lacks the capacity to adequately heat or cool homes. Since it isn’t powerful enough to create the temperatures that residents want, undersized HVAC equipment often runs non-stop. This in turn leads to higher-than-normal energy use and faster-than-normal wear. Heat pumps, air conditioners, and condensing furnaces also impact an HVAC system’s ability to regulate humidity.

If your HVAC equipment is too small, your home could feel muggy or clammy. If your indoor humidity grows too high, you may even deal with problems like mold, mildew, and pervasive, funky odors.

Although smaller units tend to be cheaper upfront, they can cost a veritable fortune to use over time when they aren’t right for their service areas. In addition to higher energy bills, frequent repairs, and all-around uncomfortable living conditions, you’ll likely have to replace an undersized HVAC system much sooner than expected.

HVAC Systems in the Goldilocks Zone

Properly sized HVAC systems offer even and efficient heating and cooling and reliable humidity control. They sustain less wear, need fewer repairs, and enjoy longer lifespans.

The Benefits of a Properly Sized HVAC System

Correct HVAC sizing offers a wealth of impressive benefits, including:

  • Enhanced Comfort: With professional HVAC sizing, you can expect even air pressure, consistent air delivery, and uniform temperatures throughout all building areas. Proper HVAC sizing prevents hot and cold spots.
  • Enhanced Efficiency: HVAC systems in the Goldilocks Zone cost less than oversized and undersized units. With fewer and more effective heating and cooling cycles, your HVAC system will use less energy. In addition to smaller, monthly energy bills, you can also enjoy a smaller carbon footprint.
  • Greater Longevity: Modern furnaces, heat pumps, and ACs can last up to 20 years. However, this is only true with correct HVAC sizing.
  • Improved Indoor Air Quality (IAQ): Better humidity regulation from heat pumps, ACs, and condensing furnaces will stave off problems like mold and mildew. Balanced air pressure will optimize the performance of your HVAC air filter so that it extracts more dust, dander, pollen, pet hair, and other airborne particulates.

How to Find HVAC Equipment in the Goldilocks Zone

So, what’s the best way to determine the right HVAC size? Consider the following:

Professional Load Calculation With the Manual J

HVAC professionals calculate the air pressure required to distribute heated or cooled air throughout homes. They use the Manual J Load calculation. This accounts for:

  • Air duct sizes, materials, and design
  • Window sizes, types, and locations
  • The number of household residents
  • Insulation types and amounts
  • The layout of the buildings
  • The square footage of living areas

If you’re tempted to shop for a heat pump or AC on your own using the total square footage of your home as your sizing guide, you risk getting equipment that’s far too large or too small for your needs.

SEER and AFUE Ratings: Your Guides for Efficiency

SEER (Seasonal Energy Efficiency Ratio) ratings are also helpful when choosing high-performing HVAC equipment. A SEER rating denotes how well an HVAC system converts energy into cooled air. Shopping for an air conditioner with a high SEER rating will limit your energy spending over the next decade. When searching for a new heater, you want a furnace with a high annual fuel utilization efficiency (AFUE) rating.

Don’t Rely on Your Old System for Sizing Information

You might think that matching the size/capacity of your old HVAC equipment is a sure way to reach the Goldilocks zone. However, there’s a good chance that your current equipment wasn’t sized correctly or that your heating and cooling needs have changed. Finishing your attic or basement, adding to the building, or completing other major renovation projects can have a significant impact on your capacity requirements. The best way to ensure proper sizing for any new HVAC installation is by starting with a professional load calculation.

Let Aztil Air Find Your “Just Right”

At Aztil Air, we know just how important a properly sized HVAC system is for efficiency, comfort, and performance. You can count on us to quickly and accurately determine your HVAC capacity needs. We can also help you choose the perfect heating and cooling equipment for the Florida climate and its heating and cooling seasons. Get in touch with us today to schedule a consultation appointment.

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What Our Clients Think Of Us


Jordan was excellant. Went above and beyond listening and talking me through everything.
Thank you Alex who diagnosed my AC issue quickly,! your superior technical skills and customer service have not gone unnoticed. Alex made my experience a pleasant one, even though my AC motor went and it needs to be ordered, the good news is it’s under warranty🤷🏼‍♂️
Today I had a repair/replacement done by Alex Molina
Alex is knowledgeable and explains what has to be done and it will be done
He is very polite, cleans up after himself and never complained about being in the sun for the number of hours that he had to be there to work
If anybody needs work and is lucky enough for Alex Molina to be your tech all will be done right
Thank you, Alex
On the ball. Courteous and efficient. Initially forgot to install cement pad, but did so when deficiency pointed out to him. Generally very pleased.
Michael King gave me outstanding service for a recent maintenance visit. He is informative, polite and above all professional. He answered all my questions and gave me good tips for ongoing maintenance.
Good job
They were excellent
Response from the owner:Hi Norman, thank you for your kind words! We're so glad to hear that Aztil did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Alez molina was excellent! Kind, proficient and efficient. Worked quickly. Am so grateful.
Response from the owner:Hi Diana, thank you for your kind words! We're so glad to hear that Alex did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Jordan & Herolson did a great job cleaning my ductwork. They arrived on time, were very nice, polite & efficient. Jordan explained everything clearly. They cleaned up thoroughly when they were done. The popcorn from my ceilings was everywhere, but they took care of it. Five stars.
Response from the owner:Hi Lisa thank you for your kind words! We're so glad to hear that Jordan and Hero did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Niko is always a competent , pleasant professional who assists me with my air conditioning units.

AZTIL responds to my calls in a timely manner.
Response from the owner:Hi Debra, thank you for your kind words! We're so glad to hear that Niko did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Jordan an hero where effective angel. They explained evdrthing and extremely pleasant
Response from the owner:Hi Carol, thank you for your kind words! We're so glad to hear that Jordan did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Tino was friendly, professional and very helpful
Response from the owner:Hi Karen, thank you for your kind words! We're so glad to hear that Tino did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Dana was great!! Suggested a cut off switch to stop the water backup
Installed it right away
Response from the owner:Hi Mel, thank you for your kind words! We're so glad to hear that Dana did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Aztil is always so reliable.
Dana came today, diagnosed my A/C problem and took care of right away.
Terrific service! Thank you, Dana!
Response from the owner:Hi Susan, thank you for your kind words! We're so glad to hear that Dana did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Best workers, Jordan,and Hero.
Response from the owner:Hi Virginia, thank you for your kind words! We're so glad to hear that Jordan and Hero did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Thanks to Aztil AC! One of our A/C units broke down unexpectedly, and Anthony got Lazaro out to us right away the next morning. Lazaro was excellent and he found the problem with our unit very quickly. We really appreciate their quick action and professional expertise. Outstanding service from start to finish!
Response from the owner:Hi Jake, thank you for your kind words! We're so glad to hear that Anthony and Lazaro did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Just has Dana come as soon as Aztil can get there team there for our family. Dana was friendly, professional and knew his stuff.
Response from the owner:Hi Justin, thank you for your kind words! We're so glad to hear that Dana did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
The AC maintenance service was excellent. Niko Garza was professional, helpful, kind, and was instrumental in arranging for the next Senior Technician to solve the AC problem that I am having. That service will be sometime today. He also recommended the dryer vent cleaning and the in-line AC cleaning, of which I scheduled for Monday and paid today. My husband has been very ill for the past 4 years and in the hospital right now. Aztil has arranged the services, after Niko explained the situation, so that they will be completed before he comes home because a patient on oxygen and a feeding tube cannot be without power to the whole house, even a short shut down would endanger him. Thank you Niko!

Technician Rick Cochran did an excellent job replacing the AC breaker and ensuring that everything was in correct working condition. I really appreciated his kindness and professional demeanor. Thank you Rick!

Today Technician Alex Molina completed the services (dryer lint trap cleaning and inline air handler cleaning). Once again, I was fortunate to have a professional, gracious, and thoughtful person come to my house to perform the services. Thank you so much Alex!

June 2 2025 Thank you Cody! It is a relief to finally have the A/C back to what it should be. The replacement of the coil is probably what was needed a month ago. Rather than dwell on what was, I truly appreciate the replacement service and how kind you were to a grieving widow.
Response from the owner:Hi Admonis, thank you for your kind words! We're so glad to hear that Niko did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Angel and his crew
Response from the owner:Hi Don, thank you for your kind words! We're so glad to hear that Angel did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Tino Costanzo did an excellent job. Extremely helpful in adding to the efficiency of the operation of our air conditioning unit.
Response from the owner:Hi David, thank you for your kind words! We're so glad to hear that Tino did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
This is the second time Michael King has serviced my AC for AZTIL. He is always pleasant and courteous. He explains all he does to the unit and answers all questions I may have. He is very thorough. Great asset to the company. The trainee (Skyler) with him today has a very good teacher and seems to be on his way to being a positive service tech.
Response from the owner:Hi Walter, thank you for your kind words! We're so glad to hear that Michael and Skyler did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Response from the owner:Hi Steven, thank you for your kind words! We're so glad to hear that Aztil did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Lazaro was excellent. Full explanation of services. I would like to get him for any future services. I'd like to add that I was pleased with the vent cleaning that was performed by Alex Molina and his assistant.
Response from the owner:Hi Jazziz, thank you for your kind words! We're so glad to hear that Lazaro did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
I had woken up to no ac in my house. I contacted aztil on a Saturday at 5 pm and their technician called me back within a half hour. His name was Tino, he said that he would be there within 30 minutes…. And he was! He figured out the problem in 10 minutes and he solved it! Excellent service! Thank you so very much!
Response from the owner:Hi Patricia, thank you for your kind words! We're so glad to hear that Tino did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Wow, the scheduling process was a challenge, but our service tech Niko Garza was a grand slam. He more than made up for the scheduling challenges. We’ve been Aztil customers since 2017…. Scheduling was much stronger up until about a year ago, service techs have always been great. Peter, one of the schedulers also can in for the save!

Hey I need to update this 5 Star review, it needs to be a 10…. We needed a new system, boom, done in one day! Our tech, Asiel Barreto was tremendous. He even worked us through the process of using a NEST thermostat- Jackie in the central office rocked us through all the paperwork. This is why we are Aztil for life!
Response from the owner:Hi Ray, thank you for your kind words! We're so glad to hear that Niko did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Jordan was awesome. Nice to work with, fast and efficient.
Response from the owner:Hi Jeffrey, thank you for your kind words! We're so glad to hear that Jordan did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Ramon is always on time, polite, knowledgeable and efficient. AC unit has been performing reliably and efficiently.
Response from the owner:Hi Lance, thank you for your kind words! We're so glad to hear that Ramon did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Nico was very knowledgeable and did a great job getting our ac working again
Response from the owner:Hi Chloe, thank you for your kind words! We're so glad to hear that Niko did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
A+ job from two great professionals - Jordan and Hero. A big job - that they explained completely - and they were not only great technically, but very tidy and cleaned everything up after! And really great guys! Highly, highly recommend them - a great team!
Response from the owner:Hi Madelyn, thank you for your kind words! We're so glad to hear that Jordan and Hero did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
TINO from Aztil is very professional he came and replace a part under warranty at no cost and in no time Aztil is very reliable I’m a happy customer thank you very much for a great service
Response from the owner:Hi Halz, thank you for your kind words! We're so glad to hear that Tino did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Nico my service tech was very knowledgeable, courteous and thorough. Very pleased with my service.
Response from the owner:Hi Jerry, thank you for your kind words! We're so glad to hear that Niko did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Response from the owner:Hi Beth, thank you for your kind words! We're so glad to hear that Aztil did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Dana & Michael did an excellent job replacing my drain lines. They arrived on time & worked hard to finish the job in record time so I was without air conditioning in 1/2 the time expected!
Response from the owner:Hi Lynda, thank you for your kind words! We're so glad to hear that Dana and Michael did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Dana and Niko were great. They did a really good job.
Response from the owner:Hi Franny, thank you for your kind words! We're so glad to hear that Dana and Niko did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Antonio & Jordan are highly professional maintenance technicians. They performed a full system overview and my AC is working great! I highly recommend them - Jeff Steinberg
Response from the owner:Hi Paul, thank you for your kind words! We're so glad to hear that Antonio and Jordan did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Luzaro did an excellent job. He got to the problem quickly and is very knowledgeable. Great service. Thank you
Response from the owner:Hi Sherry, thank you for your kind words! We're so glad to hear that Lazaro did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Update: I had Left. A bad review for this company. I had the new manager Anthony reach out to me and he helped me get my whole situation fixed. The solution was to switch back to a basic AC model that would benefit me and also be easy to work on. Anthony was great! He returned all my calls in a timely manner and helped ease my worries. Aztil finally switched out my unit and refunded me the difference. The installers were great and my experience was stellar. Def changed my look on the company. I appreciated the customer service and the communication. New management made a difference.

Previous review 3/2025
This company is the worst!! The previous AC that I used Was sold to them and I thought I could Trust them like the last company! I spent Over 12k for a unit in May 2024 along with a 5yr service contract!!! that the salesman said would be the best unit and solve all my hot spot issues. Well it hasn’t! And because my “best” unit is digital NO TECHNICIAN knows how to work the unit. They are constantly calling tech support and still no one knows. I’ve had 4 different technicians here and no one knows what the hell they are doing!! I have Had technicians out 7 times to my home bc the humidity stays at 65-68%. No one knows how to adjust it. I called For emergency service on a Friday night bc my unit stopped working. They told me they wouldn’t have anyone until Thursday!! Do not use this company. They never call you back. Management does not respond. So unprofessional! I have Been trying to contact someone for over a week and no one ever returns my calls!! DO NOT USE THIS COMPANY.
Response from the owner:Hi Myra, thank you for your kind words! We're so glad to hear that Aztil was able to address your concerns and that you were pleased with the outcome. Thank you for being a valued customer.
I've been using Aztil for over 10 years. Always prompt, polite, knowledgeable, and professional. Today (Memorial Day), my AC went out. Within 2 hours, Albert was at my house and fixed the issue quickly. I would recommend Aztil to anyone based on my own personal experience with them.
Response from the owner:Hi Demora, thank you for your kind words! We're so glad to hear that Albert did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
The 4-stars is because I wasn’t informed of a scheduling change. After a little confusion regarding the appointment time the technician, Michael King contacted me. He arrived at the updated time. Was very professional and kept me informed about the service. He completed the job, cleaned up afterwards and thanked me for being a customer.
Response from the owner:Hi Bob, thank you for your kind words! We're so glad to hear that Michael did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
My service call was simple just clean the pipes. I asked the agent what was covered before I accepted and they stated clearing the pipes and other checkup. Well it did not turn out to be TRUE. I was charged for labor , materials(!) and other nonsense. NOT a Happy camper no one likes surprises! They are out of my list.
Response from the owner:Hello Cesar, Thank you for taking time to provide feedback about your experience with our company. We completely understand your frustration and apologize for any dissatisfaction that may have caused your day. We are eager to discuss this experience with you. Please call our customer service manager, Jack. He can be reached at (561) 202-8726. It is our goal to make sure we resolve any issue we can and look forward to speaking with you.
It always seems that the air conditioner breaks down on a hot day.
Well, Aztil is cool under pressure.
First, Paul came out and diagnosed the problem and ordered the replacement parts. Making sure I got the best price.
Then, Dana showed up at my house ready to fix it.
And when it seemed things weren't quite right, Dana returned at 7:30 pm. - ON A FRIDAY NIGHT - to make sure it was A-Okay.

Aztil is definitely the company for our household.
Response from the owner:Hi Robert, thank you for your kind words! We're so glad to hear that Paul and Dana did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Michael King did a superb maintenance job. Plus, he made an extra effort to locate and install a part several hours after his first visit. Well done, Michael.
Response from the owner:Hi George, thank you for your kind words! We're so glad to hear that Michel did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Dana was tech

Came out and went through central system and outside unit. Replaced thermostat as wasn’t reading correctly which was throwing hvac off from normal operation temps
Response from the owner:Hi Andrea, thank you for your kind words! We're so glad to hear that Dana did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Dana Dussaualt did a great job on are annual maintence checkup. Very detailed inspection. Aztec has all ways provided great service.
Response from the owner:Hi Joseph, thank you for your kind words! We're so glad to hear that Dana did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Jordan and hero were phenomenal sealing my air duct system and cleaning my ducts very professional and cleaned up well thank you
Response from the owner:Hi Lynda, thank you for your kind words! We're so glad to hear that Jordan did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.
Response from the owner:Hi Michele, thank you for your kind words! We're so glad to hear that Aztil did an excellent job and that you were pleased with the outcome. Thank you for being a valued customer.

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