TNT Home Services
“I had Erick Buchlotz doing some plumbing job at my house and I was very impressed with his ability to get the job done professionally, very nice individual.”
Best HVAC Contractors in Longmont, CO
24 companies listed · 21 in Longmont · 11 open 24/7 · 13 open weekends · 23 rated 4.5+
Data verified October 27, 2026
Welzig Heating & Air
“Although installing a tankless water heater typically takes a full day, Welzig sent two technicians, Logan and his teammate, to complete the job in four hours since the work started in the afternoon.”
Colorado's Finest Heating and Air Conditioning
“I've had “Colorado's Finest” install 2 furnaces, replace my air conditioners , my kitchen sink and upgrade my water heater to a tankless version.”
Groulx Mechanical Heating & Cooling Inc.
“Mark came out to take a look at our A/C unit in our new home and he was really knowledgeable and patient in his explanation of our issues and how we should fix them!”
Blue Valley Heating & Cooling
“We had a tight time frame to work with; everyone from Cameron in sales to the technicians that were at the house today bent over backwards to make sure we made our deadline.”
KJ Thomas Mechanical
“I have used them for regular maintenance, repairs, and complete replacement of our furnace/humidifier/central air system and always happy with their work.”
The 24 companies listed for Longmont, CO work on furnaces, heat pumps and air conditioners. Each profile repeats what the company publishes about its hours, its license and the equipment it fits, alongside ratings and quotes drawn from public reviews.
Area overview: Longmont, CO
Of the 24 companies we list here, 21 are in Longmont itself and 3 come from Loveland (1, 17 mi) and Denver (1, 31 mi). The companies on this page are rated from 3.8 to 5.0 across 8,237 reviews; 14 have 50 or more reviews and 23 are rated 4.5 or higher. When customers rate these companies on specific qualities, they most often praise professionalism (89%), responsiveness (88%) and quality (82%). The topics that come up most in reviews of the companies on this page are "price", "efficient" and "estimates". 11 are open around the clock and 13 are open on weekends. The services the companies on this page list most often on their websites are commercial hvac (3), heating (3), indoor air quality (3), air conditioning (2) and heating installation (2). 9 show a license on their websites; 4 list staff certifications (NATE) and 8 have a BBB rating of A or A+. 12 have ten or more years of experience, the longest 40 years. 12 offer emergency call-outs; 13 offer financing or payment plans; 11 give free estimates; 7 are family- or locally-owned and 13 list coupons or special offers. We count these figures across the companies on this page; distances are straight-line, and hours and prices change, so confirm the details with the company before you book.
Do any heating firms listed for Longmont work on Saturdays or Sundays?
Saturday or Sunday hours show up for 13 of the 24 companies here. Saturdays fill with the calls that came in on Friday, so ask whether you are getting a repair slot or a sales visit. Sunday work is usually treated as an emergency call.
Service Experts Heating & Air Conditioning
“Recently had my yearly advantage service check done by Rich, Clem, Matt and Leo on my Furnace, heat pump, steam humidifier, tankless water heater and my halo 5 water filtration.”
M and M Heating
“He knows what he's talking about and is concise in what the issues may be with our AC system and offers solutions to these issues in a way that is easy to understand.”
Highland Heating & Air
“He knew immediately what the issue was, fixed it and took the time to explain the problem to me and give me some tips to help prevent it from happening in the future.”
Colorado Green Plumbing
“Pricing was competitive, they were able to replace our furnace quickly in the middle of a big cold snap and they left our basement cleaner than when they got there!”
Homerun Heating
“Home Run HVAC and plumbing has done exactly what their name implies; they have hit a 5 Star home run for some very difficult work in my 118 year old home.”
Everest Mechanical
“And of course we wanted to replace it with a high efficiency on-demand water heater if possible (not a great time to do the research when you have one already broken!”
My Guy Heating and Air (Longmont)
“My Guys Heating and Ait is the best company I have ever dealt with!”
Circulating Air Inc
“New furnace (understandable, it was old), new water heater (kind of suspicious, because it wasn't that old -- but ok), then saying we needed a new AC (a 7 year old unit).”
Stone Heating & Air
“I have used many HVAC contractors over the years and have finally found someone that I can rely on and that I know will be honest and fair with my clients.”
SAC Mechanical Heating & Air Conditioning
“Being in the property management business (All County Boulder Property Management Team) , I work with SAC Mechanical and their amazing staff often on a daily basis.”
Armendariz Heating and Cooling Inc
“I highly recommend Armendariz Heating and Cooling, especially if Juan and Trevor provide the service.”
Maddison Mechanical
“I seriously cannot thank them and the company enough for going above and beyond… issues like these are often frustrating to deal with but my experience with them have been nothing short of amazing.”
Vertical Heating & Cooling LLC
“Whatever your HVAC needs, he'll figure out how to solve your problems quickly and efficiently - and he'll explain everything to you so you understand it too.”
Control Service Center
“Though they do service mostly the commercial industry, they went out of their way to help out my family get a new furnace installed in our newly purchased home.”
Longmont Heating and Air Cooling Contractors
“Air Masters Heating And Cooling team is the real deal all around.”
Comfort Craft
“I had another HVAC company out to look at my AC unit that had stopped working and they told me it wasn't worth fixing and that I needed a brand new unit for around $15,000.”
Mighty Plumbing and Heating LLC
“Faucets were installed but the plumber bent the kitchen sink and I had to call a different company to come out and stabilize the kitchen sink in addition to the fixing the bathroom faucet drain that was overly tightened and damaged during install .”
Tri-City Heating & Air Conditioning Inc.
“We've used other heating and air companies in the past that only wanted to spend their time upselling a product, and not providing the service you call for.”
Why these companies made our list
What customers say about companies in Longmont
- “Super friendly, knowledgeable, and fast service techs! Worth every penny for an early winter furnace check.” — customer of Groulx Mechanical Heating & Cooling Inc.
- “Overall outstanding service from this company. Not only did they take extra time going over everything to make sure all my questions were satisfied, but the installation went smoothly and professionally.” — customer of Colorado's Finest Heating and Air Conditioning
- “Extremely responsive and respectful owner and crew. Thank you for the great service.” — customer of Stone Heating & Air
- “Karl arrived promptly, and within 10 minutes, had diagnosed and fixed the problem with our air conditioner.” — customer of KJ Thomas Mechanical
- “John Stone was able to work me into the schedule and get me taken care of, with a correctly sized furnace for my home, right away.” — customer of Stone Heating & Air
Excerpts from public reviews of the companies listed on this page.
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