Learn how to choose the right AC size for your St. Louis home. Discover why proper air conditioner sizing matters and when to schedule a consultation.
When summer temperatures rise in the St. Louis metro area, a properly sized air conditioner makes the difference between a comfortable home and one that constantly feels hot and humid.
Many homeowners assume “bigger is better” when it comes to air conditioning. In reality, an oversized system can cause just as many problems as an undersized one. If you’re considering AC replacement or a new HVAC installation, understanding how air conditioner sizing works can help you make the right decision for your home.
Update 4/6/26: Zach Sperling is such a pleasant and knowledgeable technician that I recommend him highly. Thomas Heating has been a wonderful company to work with in my maintenance plan. If you are looking for a reputable company, look no more.
This company is so responsive that I love them. They respond immediately, and I trust them to tell me what needs to be done. I haven’t been steered wrong yet. They are genuinely nice to work with and honest. I use their maintenance program which I highly recommend.
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work good but got at least 6 messages from them very annoying
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Nick was great! He came right out and was able to solve the problem fairly easily. He communicated well and helped us prevent a future problem as well.
Response from the owner:Thank you for the review, Philip! We are happy to hear you had a pleasant experience working with us.
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They have never failed to fix my hvac problems. These folks are top tier.
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Giovanni was very professional, helpful, patient and helped me figure out the issue, if it was covered under warranty, and next steps. Great overall experience and much appreciated.
Response from the owner:Thank you, Amy! We're glad to hear that Giovanni provided you with such professional and helpful service. Your appreciation means a lot to us!
Always professional and thorough whenever they service our home. We have used Thomas Hoffmann Air Conditioning & Heating multiple times since we moved into our home and will continue to use them in the future.
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0 stars if I could. Bought a faulty (not to mention overpriced) surface igniter, called back five minutes later after installing, of course they didn’t stand behind their part. Go to Grainger instead. Same (working) part, half the price.
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From the phone to the completion of the job everyone is so polite and informative. I had Giovani as our representative and he was very informative and professional, and knew exactly what the problem was. Thanks so much.
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My furnace was not working. A very nice gentleman came out this morning and fixed the problem and now I have much needed heat. He was very professional and courteous. I will definitely be using them again when the need arises.
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I will always call Hoffmans for my air and heat needs. They were out to my daughters house that day and fixed it. It was right before the weekend storm with below zero temps the next day. They saved my daughter and grandbabies. I could never thank them more.
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Snow and drifting snow covered intake and out take vents causing the furnace emergency to shut off furnace. Cleaned off the driftibg/ snow off roof and vents furnace works perfect now. Thank you and great job Nick.
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5 stars! Nick was here to fix my heater within 2 hours of my call. He explained the problem to me thoroughly and got the job done quickly & professionally. Thank you so much!
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Extremely thorough and educational. They do a wonderful job of explaining everything and making sure I was comfortable knowing how the systems worked in my house!
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I noticed a strange noise that I was concerned was linked to my furnace. I called Thomas Hoffman Heating & Cooling and Nick came right out. He was very thorough checking all components. Thankfully all checked out for us this visit. Definitely recommend Thomas Hoffman Heating & Cooling!
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Thomas Hoffman is a wonderful company to work with. Techs are knowledgeable, personable & efficient.
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Got a quote over the phone. Everything was explained thoroughly. Dakota, my technician arrived and on time, was very professional and knowledgeable. He didn’t try to upsell or change anything. He did a great job. We can already tell the difference since the ducts and vents were cleaned. Would recommend an use Hoffman again in the future.
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The technician, Ryan, was knowledgeable and helpful in identifying the issue with our mini split AC unit. They are the second company we called after issues with the first and will be using Hoffmann again.
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woke up to a very cold house, called Thomas Hoffmann, they were able to come out a couple of hours later and get the issue resolved. Always trust them, they have always been quick to respond and get either the heating or ac issue fixed that day. Also a great price!!!! give them 10 stars if i could, Thank You JS
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The technician Giovanni was excellent and on time very professional and efficient and knowledgeable of the project at hand ,gave great advice but most of all did great work 👏 thank you .
Response from the owner:We are so happy to hear you had a great experience, Sam! Thank you for the review, and thank you for your business.
Why Proper AC Sizing Matters
Choosing the right size air conditioner is one of the most important factors in home comfort and energy efficiency. A system that is too small will:
Missouri summers are hot and humid, so proper sizing is especially important in St. Louis homes.
How Air Conditioners Are Sized
Air conditioners are not sized by square footage alone. They are sized by cooling capacity, measured in BTUs (British Thermal Units). Most residential systems are also described in tons of cooling capacity. Here’s how that works:
AC Size
Cooling Capacity
1.5 ton
18,000 BTUs
2 ton
24,000 BTUs
2.5 ton
30,000 BTUs
3 ton
36,000 BTUs
4 ton
48,000 BTUs
5 ton
60,000 BTUs
The “ton” rating does not refer to weight. It refers to the amount of heat the system can remove from your home.
Typical AC Sizes Based on Home Size
While every home is different, these estimates provide a general guideline.
Home Size
Typical AC Size
900 – 1,200 sq ft
1.5 – 2 tons
1,200 – 1,500 sq ft
2 – 2.5 tons
1,500 – 2,000 sq ft
2.5 – 3 tons
2,000 – 2,500 sq ft
3 – 3.5 tons
2,500 – 3,200 sq ft
3.5 – 4 tons
3,200 – 4,000 sq ft
4 – 5 tons
However, square footage alone is not enough to determine the correct AC size. Professional HVAC companies perform a detailed analysis to calculate the exact capacity your home needs.
Why Oversizing Is a Common Problem
Unfortunately, some HVAC installations skip the proper calculations and simply replace the old unit with the same size. This can cause problems because:
Older homes may have been improperly sized originally
Renovations may have changed the home’s cooling needs
New equipment operates differently from older systems
Why Homeowners Choose a Local St. Louis HVAC Company
Choosing the right HVAC contractor matters just as much as selecting the right equipment. Working with a locally owned St. Louis HVAC company ensures:
Technicians familiar with the Missouri climate
Personalized service
Proper system sizing
Reliable installation
National companies that appear local online often rely on large call centers and subcontractors. Local companies are invested in the community they serve.
Schedule an AC Sizing Consultation in St. Louis
If you’re planning to replace your air conditioner or want to confirm your system is properly sized, a professional evaluation is the best place to start. The team at Thomas Hoffmann Air Conditioning & Heating LLC provides expert AC installation and replacement services throughout the St. Louis metro area. Call today for AC service or replacement consultation:(314) 471-7625
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At Thomas Hoffmann Air Conditioning & Heating, we pride ourselves on being a locally owned and operated HVAC company. With more than 30 years of experience and a master technician and mechanical engineer as our owner, we can replace, repair, and maintain your business or home’s HVAC system.
