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Should You Choose a 5000 BTU AC? | St. Louis HVAC Sizing Guide

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As summer heat hits hard across Missouri, homeowners look for quick, affordable cooling solutions.

They often land on small windows or portable units labeled “5000 BTU.” But what does that actually mean?

At Thomas Hoffmann Air Conditioning & Heating, we always get this question: “Is a 5000 BTU AC enough to cool my room?”

Signs It's Time to Replace AC System
Teresa F.
2 days ago
Our service technician arrived right on time and was professional, friendly, efficient and courteous. We couldn’t ask for more.
Response from the owner:Thank you for sharing your positive experience with our service technician! We appreciate your kind words and are glad to hear that you were satisfied with the service provided.
Marilyn H.
6 days ago
Nick was was great! He provided great service, explained everything, and was patient and kind.I definitely recommend using Hoffman!
Response from the owner:Thank you, Marilyn! We're glad to hear that Nick provided you with excellent service and made your experience enjoyable. We appreciate your recommendation!
Jasmine W.
7 days ago
The whole team was great, professional and friendly. Scheduling was easy and well organized, they had many options for different price points and financing options. Thank you!
Response from the owner:Thank you for the thoughtful review, Jasmine! We appreciate your support and continued business.
Henry D.
7 days ago
I have complete trust in Thomas Hoffman AC . I have had multiple
technicians who are always polite and knowledgeable.
Response from the owner:Thank you for your trust in our team, Henry! We appreciate your kind words about our technicians.
Theresa S.
2 weeks ago
Love that it’s the same technician every time. Let’s me know what he found and any concerns he might have regarding our units. Great customer service.
Response from the owner:Thank you, Theresa! We're glad to hear you appreciate having the same technician and the communication about your units. Your feedback on our customer service means a lot to us!
Frank P.
2 weeks ago
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.
Response from the owner:Thank you for the kind review, Frank! We appreciate you and your business.
Allan G.
2 weeks ago
Zach did an excellent job! Always courteous and friendly. We would highly recommend calling Thomas Hoffmann HVAC for any heating and cooling needs.
Response from the owner:Thank you, Allan! We're glad to hear that Zach provided excellent service and appreciate your recommendation for Thomas Hoffmann HVAC.
William W.
2 weeks ago
Was able to locate the problem right away and replace a switch and add Freon very nice job by this employee. I will recommend Thomas Hoffman for future references.
Response from the owner:Thank you, William! We're glad to hear that our team was able to quickly address the issue and that you had a positive experience with Thomas. Your recommendation means a lot to us!
Jack D.
2 weeks ago
I had Nick come out. He was awesome. Very knowledgeable, prompt and helpful. I will definitely recommend Thomas Hoffmann HVAC to others in need of HVAC support.
Response from the owner:Thank you, Jack! We're glad to hear that Nick provided you with excellent service. We appreciate your recommendation and look forward to assisting you and others in the future.
FFE L.
2 weeks ago
From our initial quote until the new furnace and AC were completed, everything was smooth and efficient. Zachary and Giovanni were excellent on-site, taking time to explain the installation as well as leaving the home clean.
Thank you Thomas Hoffmann team
Response from the owner:Thank you! We're glad to hear that the installation process was smooth and efficient. Zachary and Giovanni will be pleased to know their efforts made a positive impact. We appreciate your kind words about the team!
Bob De P.
2 weeks ago
Courteous friendly and efficient! What else could you want!
Response from the owner:Thank you, Bob! We're glad you found our service courteous, friendly, and efficient – that's exactly what we strive for!
Princess C.
2 weeks ago
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.
Response from the owner:Thank you for your kind words, we truly appreciate your trust in us and are glad to hear about your positive experience with our services.
Julie N.
3 weeks ago
So helpful! Straight into the point with no runaround or Negotiating up sells! Quick and efficient!
Response from the owner:Thank you for the great review, Julie! We appreciate your business and the support!
George G.
3 weeks ago
Great fast courteous service, knowledgeable.
Response from the owner:Thank you for recognizing our fast and courteous service, we appreciate your feedback!
harold B.
3 weeks ago
work good but got at least 6 messages from them
very annoying
Response from the owner:Thank you for your feedback, Harold. We appreciate your input and understand how too many messages can be frustrating. We'll work on improving that experience for you.
Philip D.
4 weeks ago
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.
Pat Keith T.
4 weeks ago
Geovanni is great!
Response from the owner:Thank you, Pat, for your kind words about Giovanni; we appreciate your feedback and are glad to hear that he made a positive impression.
Greg D.
4 weeks ago
They have never failed to fix my hvac problems. These folks are top tier.
Response from the owner:Thank you for the wonderful feedback, Greg! We're glad to hear that you've had such positive experiences with our team. Providing timely and effective service is our priority, and we're here whenever you need us. Looking forward to assisting you again!
Amy K.
1 month ago
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!
Joe G.
1 month ago
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.
Response from the owner:Thank you for the thoughtful review, Joe. We appreciate you and your business!
Daniel D.
1 month ago
Met Nick at ACCA - conference for HVAC contractors. He’s an expert! 100%
14 years in the business, doing a great job and service.
Response from the owner:Hi Daniel! So happy to hear you enjoyed Nick's company. We are lucky to have him.
Kelly R.
1 month ago
Very easy to work with. Technician kept me informed about what was going on through the whole process.
Response from the owner:Thank you for the great review, Kelly! We appreciate your business.
Jordan P.
2 months ago
Nick was awesome! He was extremely professional and answered any questions I had. Would highly recommend!
Response from the owner:Thank you for your kind review, Jordan! We are happy to hear you had a great experience using Thomas Hoffmann.
Jill P.
2 months ago
Got the job done fast and explained every step as it was happening!
Response from the owner:We are happy to hear you had a great experience! Thank you for the kind review.
Veronica V.
2 months ago
We have a tankless water heater that needed cleaning and a new part, they came out very quickly and got the hot water back again. Thank you!
Response from the owner:We are happy to hear you had a pleasant experience! Thank you for the kind review, and your continued support.
jay70001
3 months ago
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.
Response from the owner:Hi there. I am unable to locate your customer profile. Please give our office a call at 314-471-7625 so we can get this figured out for you.
Katherine T.
3 months ago
Always a great experience. Was able to get out same day to help, knowledgeable of old homes, including their systems and new systems as well.
Response from the owner:Thank you for your kind review, Katherine! We appreciate your business.
April T.
3 months ago
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.
Response from the owner:Thank you for the positive feedback! We're glad to hear that you were pleased with our prompt and friendly service. We look forward to assisting you again in the future!
Kathleen D.
3 months ago
Ryan was very professional, knowledgeable, and thorough. I was able to get an appointment the same day during a biter, snowy day.
Response from the owner:We are so glad to hear you had a pleasant experience, Kathleen!
Melinda D.
3 months ago
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.
Response from the owner:We are so happy to hear that we could help! Thank you for the kind review.
Scott S.
3 months ago
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.
Response from the owner:Thanks for the great review, Scott! We appreciate your support.
Jessica B.
3 months ago
Came during a storm with emergency call for heat- did a quick and fast job getting furnace running! Whoot!
Response from the owner:Thank you for the great review, Jessica! We appreciate your support.
Jennifer H.
3 months ago
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!
Response from the owner:Thank you for the kind review, Jennifer! Glad we could help.
Matthew B.
3 months ago
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!
Response from the owner:Thanks for the great review, Matthew! We appreciate your support.
Joe C.
3 months ago
Nick did an amazing job, on time, very knowledge and professional.
Response from the owner:Thank you for the great review, Joe. We look forward to servicing you in the future!
anna M.
3 months ago
installed humidifier and hepa filter. Very pleased with service.
Response from the owner:We are happy to hear that you had a pleasant experience!
Abby C.
3 months ago
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!
Response from the owner:Thank you so much for the kind review, Abby! We appreciate your business and look forward to servicing you in the future.
DA O.
3 months ago
I would describe the overall experience as professional, but also kind and responsive from the initial phone call to the technician.
Response from the owner:Thank you for your kind review! We appreciate your business and look forward to helping you in the future.
Christine G.
3 months ago
Thomas Hoffman is a wonderful company to work with. Techs are knowledgeable, personable & efficient.
Response from the owner:Thank you, Christine, for your kind words about our team; we appreciate your feedback and are glad to hear you had a positive experience!

What Does 5000 BTU Mean?

BTU stands for British Thermal Unit, a measurement of energy. In air conditioning, it describes how much heat a unit can remove from a room per hour. So, a 5000 BTU AC removes 5,000 BTUs of heat each hour.

The higher the BTU, the more powerful the air conditioner.

Is 5000 BTU Enough for Your Space?

A 5000 BTU unit is best suited for small spaces like:

  • Bedrooms up to 150 square feet
  • Small offices
  • Dorm rooms
  • Studios
Indoor Air Quality St. Louis

Quick AC Sizing by Room Size:

Room Size (sq. ft.)Recommended BTU
Up to 1505,000
150 – 2506,000
250 – 3007,000
300 – 3508,000
350 – 4009,000 – 10,000

Pro Tip: Always size based on the usable square footage, factoring in insulation, sun exposure, and ceiling height.

When 5000 BTU Is Not Enough

Even if you’re cooling a small space, 5000 BTUs might not cut it in some instances:

  • South-facing windows or heavy sunlight exposure
  • Rooms with poor insulation
  • High ceilings
  • More than two occupants are regularly inside the room

If your system is underpowered, it will run constantly without reaching the set temperature, wasting energy and wearing out early.

Window vs. Portable: Which 5000 BTU AC Is Better?

Both can work for small spaces, but:

  • Window Units: More efficient, quieter, better for permanent installations.
  • Portable Units: Flexible, easy to move, louder, and usually less efficient.

Still unsure? Our local team can help recommend the correct setup for your home and budget.

Whole-Home AC vs. Room Units

If you’re using multiple 5000 BTU units around the house—or if one room always feels too warm—it may be time to consider a central AC upgrade or ductless mini-split system.

These systems offer:

  • Better energy efficiency
  • Consistent temperature across rooms
  • Cleaner indoor air
  • Smart thermostat integration

We offer free consultations for homeowners in St. Louis, Kirkwood, Ballwin, and surrounding areas.

St. Louis’s Trusted Cooling Experts

At Thomas Hoffmann Air Conditioning & Heating, we help Missouri homeowners make wise, cost-effective cooling choices. Whether you need help sizing your system or want a full-home upgrade, our local team is here for you, not a national call center.

24/7 Service Call Now

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.

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