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About Grenz Service Company LLC

Excellence Since 1987

As a family-owned and operated business, we’ve proudly served the Waukesha and Jefferson County areas, delivering friendly, dependable heating and cooling solutions to both homes and businesses.

Our Mission

Our mission is to provide top-quality HVAC services with integrity and a personal touch. Led by founder Jim Grenz, Sr., and his son Jim Grenz, Jr., we specialize in:

Commercial and residential service on all makes and models
Air conditioner and furnace repair
Maintenance on all brands of air conditioners, heat pumps, and furnaces
Installation and service on commercial refrigeration equipment, including walk-in and reach-in freezers and coolers, back bars, and ice machines
Gas fireplace service and maintenance

Our continuously trained staff is always ready to answer your questions, ensuring you receive the most performance, value, and peace of mind possible.

What Sets Us Apart

Reliability: You can count on us to be there when it matters most.
Transparency: Clear communication and honest pricing come standard.
Expertise: Our team undergoes rigorous training to stay updated with the latest HVAC technologies.
Customer-Centric Approach: We treat our customers the way we’d like to be treated—showing up on time, being prepared, doing quality work, and treating your home as if it were our own.

Our Commitment

We are proud to be an independent dealer of Trane products, excelling in their installation and service. Our helpful staff is always on standby to answer any questions, and we offer the proven quality of top brand names to ensure that you get the most performance, value, and peace of mind possible.

Beautiful living room interior with tall vaulted ceiling, loft area, hardwood floors and fireplace in new luxury home. Has large bank of windows

Testimonials

SEE WHAT YOUR NEIGHBORS ARE SAYING ABOUT Grenz Service Company LLC

Google Rating

5.0

Based on 323 reviews

Grenz Service Company LLC

5.0

Debra Tula

17:53 14 Apr 26

Grenz has serviced my AC, heating, and gas fireplace for about 15 years.A wonderful family owned company, with old fashioned values of getting things done right the first time!

Steven

13:46 11 Apr 26

Always fair and reliable

David Medici

15:58 04 Apr 26

Grenz Service Company recently did two jobs at my home.The first was installing a new HVAC system. Jim Grenz walked me through all the options and provided me with three quotes, each depending on the low, medium, or high grade HVAC that were recommended. They answered all my questions, did the install in one afternoon, and even entertained my questions and requests for system configuration tutorial. Awesome!The second was a repair to my gas fireplace. The pilot light had just aged, and my penchant for turning off the pilot after winter was not a good idea. Again, the service was excellent.I would highly recommend Grenz Service Company. Great products, great service, great prices.

Debra Krajacic

21:10 01 Apr 26

We have used Grenz Service Company many times to perform tuneup, cleaning of glass and burners and make certain all was working well with our fireplace. Recently had a pipe burst causing a water leak resulting in water to seep under fireplace unit. Grenz contacted me the same day I called and worked an appointment to come out to make certain all was working properly. During their inspection they even found and repaired a small gas leak. They are very professional, knowledgeable, kind, and work you into their schedule quickly. They know what they are doing and have always fixed anything we needed the first time. I highly recommend any of their services.

Terry Berg

21:47 31 Mar 26

Judy B (Judy B)

00:45 30 Mar 26

We needed both central air and furnace unit. Jim came out to our home to meet with us and provided a very thorough and comprehensive explanation of his products and services. He inspected our home and gave us several options. I have NEVER met an individual so thoroughly knowledgable about the industry, their product line, and technical details. Outstanding person to work with. Very professional communication - and timely! They reminded us of their upcoming visit and provided detailed receipts. (Nothing hand-drawn here!). The install was flawless - professional and hard-working team. I sincerely wish I experienced this degree of professionalism, honesty, and expertise with each company we worked with. We are very grateful we found Jim and his team. They are now our HVAC company and we would highly recommend them to everyone. Thank you Jim!

Judy Serkosky

14:26 27 Mar 26

Leighann Moll

00:50 27 Mar 26

Excellent customer service and always ensure done right!Highly recommend.

Tee L'zee

13:11 25 Mar 26

Prompt, organized, efficient, fair price, good communications.

James Plaster

17:34 19 Mar 26

Jim Grenz provides a service that nobody else in this area does. He repaired our gas fireplace instead of us having to replace it.

Karli G

13:23 12 Mar 26

Jim Jr. was very pleasant to work with. He kept me informed with what he was doing and explained things to me in a way I could understand. Very professional and personable.

gary beres

19:53 06 Mar 26

Great service. Was able to come as soon as he could.

Chris Cordes

21:34 28 Feb 26

At this point, it looks like these folks saved me between $1,500 and $19,000, depending on which of the suggested repairs/upgrades two other companies wanted me to agree to. Nice to have this company come give me a second opinion: “If it were my furnace, I wouldn’t do anything with it. It is running fine.” So, unless the furnace fails in the next some years, I’m grateful for this company’s assessment, which appears not to be self-serving.

Kathy Roesch

22:13 25 Feb 26

Very prompt, excellent service. Very knowledgable and friendly! Thanks!

LeAnn Ozminkowski

21:02 21 Feb 26

Never had my fireplaces serviced in 25 years! Recommended by a friend, Grenz spent extra time teaching me how the gas fireplaces worked and how to maintain them. They even discovered a small gas leak and repaired it. When it is time to replace my furnace, I will give them a call.

Susan Buchanan

17:13 20 Feb 26

Jim and his associate did a wonderful job with fixing our fireplace! I highly recommend them, very professional

Raul Terriquez

01:11 20 Feb 26

Got the service the same day. Very professional and knowledgeable. Reasonably priced and overall a great company!

John Leidel

19:56 19 Feb 26

Fast, professional work. Very knowledgeable and experienced we have become a regular customer for our refrigeration needs.

Rene Greguska

17:00 15 Feb 26

Nathan Emanuel

21:33 12 Feb 26

Our boiler needed repair and Jim was able to fit us in and get it fixed very quickly. Would highly recommend!

Eric Millard

14:46 05 Feb 26

Marilyn Davis

12:33 31 Jan 26

Repaired my very old gas fireplace. Very thorough, friendly and efficient!

Tim Hetherington

18:08 29 Jan 26

I continue to use Grenz and they never disappoint. Good, honest, hardworking, reliable and knowledgeable are just a few words I don’t just throw around. Jim and all of his employees are good people and beyond trustworthy. To say I trust them is an understatement. I don’t trust too many people. I trust Grenz in my home even if I’m not there. If that doesn’t say something, I don’t know what does.Top notch service with honesty and integrity. I learned all the ins and outs about my furnace. They found a bad part and showed and explained why it was bad. The replacement part was inexpensive. Very thorough and trustworthy. All this and it won’t cost you any more than anyone else, maybe less. Grenz is the only place I’ll be calling in the future. Peace of mind is priceless!Yet another positive experience. Time after time, Grenz always comes through providing top notch service you can count on.

Michael Figueira

04:26 29 Jan 26

Paula Larsen

01:15 29 Jan 26

Great company to work with.They’re the best.

Alexander Young

21:42 24 Jan 26

Quick service, great service when our heat was not working.

Natalie Kieffer

20:10 23 Jan 26

We had probs with our furnace going into below zero temps and Grenz arrived within 2.5 hours of our call! They got our heat back on quickly!! Thanks Jim & Team for all your support!

Michael Giesfeldt

16:10 22 Jan 26

Sorry, guys forgot to add the five stars thanks again not sure if the first post went through, but just want to say great job pleasure to talk to and I would have you Recommended if someone asked

Steve Richter

00:54 22 Jan 26

Have been with Grenz for many years and have always had great service! Very reliable-honest family business!

RayL

20:47 20 Jan 26

Denise Schulz

21:54 16 Jan 26

We’ve been using Grenz for over 20 years. Jim is always responsive, friendly, and professional. Additionally, his work is outstanding.

Mark W

16:15 16 Jan 26

Grenz is by far the best. I made the mistake of having another company based out of Watertown come out for service. They said my heat exchanger was bad and I needed a new furnace because it wasn't under warranty. Called Grenz and found out it actually was under warranty so i had him come out. Extensive testing revealed that it was not the heat exchanger after all. Simple part replacement saved me thousands of dollars. From now on I will be making only one call to Grenz.

Joe Verhagen

21:38 15 Jan 26

Very communicative prior to arriving. Explained everything while here, very well. Work was quick& to the point, was detailed. Fireplace now works great!

Ron Stortz

18:26 15 Jan 26

Bought an ice making machine for the bar in the basement. Very professional service, great communication thru the entire process, and the quoted price and actual price was dead on. Highly recommend

Larry Gardner

16:54 12 Jan 26

Great, friendly, professional.

Heidi Olson

22:59 11 Jan 26

Thorough. Problem solved until fireplace was working properly. Reasonably priced.

Therese De Rosier

19:11 11 Jan 26

Fireplace tune-up

Laurie Wilson

16:26 04 Jan 26

Our two furnaces had a catastophic fail late on Christmas Eve and we needed emergency service. Jim Grenz made a service call to our home early on Christmas Day and was able to install new furnaces on the day after Christmas. Jim was extremely responsive and understanding to our emergency call. Grenz service was extemely responsive and they went above and beyond to handle our emergency. We would highly recommend Grenz Service as you will find them dependable, responsive, honest and knowledgable!

Michael Steger

23:53 31 Dec 25

Grenz gives excellent, professional and maybe the most important, Fast Service. I can always depend on them to get me out of a tough spot. Thank You!

christy dawson

22:59 31 Dec 25

Always prompt, thorough, and trustworthy service!

Darrel Fernandez

23:27 29 Dec 25

Fireplace, cleaning?

Jerry Boll

21:36 22 Dec 25

Very thorough service with great communication and knowledge shared!)

M K

21:52 20 Dec 25

Quality work. Reliable service. Decent people. Highly recommended.

Stephen Lauber

14:51 20 Dec 25

Steve Knoebel

14:12 20 Dec 25

Thermostat installed

Michael Strauss

14:08 19 Dec 25

Jim Jr was great to work with had us going very quickly

Brad Murray

19:22 18 Dec 25

Sohinder Singh

14:45 16 Dec 25

Rick Budde

14:45 16 Dec 25

I was very pleased with Grenz Service. Jim quickly diagnosed the problem with my furnace and was able to get the needed parts and complete the repair the same day. He explained how my system works and politely answered all of my questions. I will not hesitate to call Grenz in the future.

john chatham

00:18 13 Dec 25

Same day response. Awesome

John Burow

22:18 12 Dec 25

Kathy Mitchell

21:30 10 Dec 25

Frank Briscoe

04:06 05 Dec 25

Worked on our gas fireplace to ensure that it was in good working shape. Cleaned the glass and added a monitor (?) to the fan so it is now very quiet. On time, friendly and excellent work.

robert spors

04:23 03 Dec 25

We just had a full heating and air system installed by Grenz Services recently. This company and the individuals involved were very knowledgeable and highly professional as they arrived on time and completed all work in a timely and very impressive manner. They also were very helpful and friendly throughout. Our new system is working beautifully just in time for this very cold December. We recommend highly!

15:23 29 Nov 25

22:36 26 Nov 25

17:29 23 Nov 25

16:34 22 Nov 25

The process from scheduling to notifying me via text the day of our appointment, everything went so smoothly. The glass on my fireplace was cleaned so well and we are thrilled that our fireplace is working again.

Joe Anderson

14:57 21 Nov 25

Very timely, responsive. Had heating back up and running sooner than I expected. Great experience.

Justus Klink

16:07 19 Nov 25

Paula Zibton

21:50 15 Nov 25

Have used Grenz for our hot water heater and furnace needs for years and have always been extremely impressed. Wonderful to work with.

Daniel Ayala

00:56 14 Nov 25

Fantastic experience with Grenz. Easy to talk about what we were looking for. They completed everything the way they said it would be done. Showed up on time and the whole team was really respectful. Great group of people. Thanks Jim!

Mackenzie Edinger

01:53 13 Nov 25

Every time I need them, they are out SO quick and the job is always done thoroughly.

George Pavin

22:33 12 Nov 25

Dave Hohisel

00:05 10 Nov 25

Very knowledgeable and fair business. Highly recommend!

William Seymour

23:12 09 Nov 25

The service Jim provided in tuning up our fireplace for the season was top notch! Thank you!

Mike Kujawa

00:44 09 Nov 25

Barbi Nash

19:30 07 Nov 25

Very friendly and incredibly prompt!!!

ken angus

19:30 07 Nov 25

Everything went great 👍 On time and everything looks good.Thank you Grenz!

Pat Lavelle

22:05 05 Nov 25

Did a great job - fireplace looks better than the day we first used it! Very happy with the service!

Amanda S

21:45 05 Nov 25

Grenz is a great company to work with. They are quick to get back to you with any questions. They do quality work and in a timely manner. They are kind, helpful, give thorough explanations, and answer all my questions! I can’t say enough good things about Grenz. We have had furnaces serviced and replaced as well as humidifiers. They are a top notch company that we will continue to work with. Look no further for a trustworthy, hardworking, honest company.We have been working with Grenz for years now and we still feel the same way! They are great to work with. Thank you!

jean hicks

02:13 05 Nov 25

Boiler tune up and replaced condensate pump. Fit me into the schedule early, explained the work being done, neat, and efficient.

mary cunningham

23:41 04 Nov 25

As usual Junior was here with a quick fix so we’re not freezing! Always prompt! Always cheerful! Never wrong! Bravo Grenz!

John Urbalejo

22:06 03 Nov 25

Grenz Service Co came here and took care of my gas fireplace. Explained everything with patience and understanding so that my wife could fully understand and she was completely happy and satisfied. I was at work when she called me and told me how comfortable she felt with their service and how happy she was with them. And as we all know if wife is happy, I am happy.

Liz

21:22 02 Nov 25

I initially had Grenz Service come into my condo to check my fireplace and clean the glass. They had done such a great job I inquired about heating and air conditioning. I really liked all the information I received about the fireplace, heating and air conditioning I thought I would give them a try. This is my fifth year with them. They are very thorough and there is never a mess. I would recommend Grenz Service to anyone looking for a dependable company year after year.

Hollis Cloninger

13:57 27 Oct 25

Amazing service! Always professional and reliable!

Michael Tessereau

19:25 25 Oct 25

Two furnaces serviced and two air conditioners to be serviced in spring paid for. Been using Grenz for 28 years and am completely satisfied. Tech Connor knows his stuff and lets me watch. Never know what I might learn..

Craig Kuhary

19:39 22 Oct 25

We have had Grenz maintain, service and install our major appliances for almost 30 years. They have never failed to deliver on quality and responsiveness. The only time I didn't listen to their advice and scrimped on cost (and quality) I was left disappointed and with a product that didn't last. We had Grenz come in and correct it to our complete satisfaction. You will not find a more experienced team!

Aaron Jambura

00:52 22 Oct 25

Robbie Geboy

18:14 18 Oct 25

My furnace went out. I called Jim. My furnace was up and running the same day. These men are great and honest which is hard to find these days. Thanks again for great service.

Ralph Galdieri

00:04 17 Oct 25

Michael Remitz

13:41 16 Oct 25

Best service in town and very good people

Todd Anderson

02:04 15 Oct 25

After review and a few quotes/consultations, I chose Grenz Service to install a new Trane furnace and AC. Jim was extremely helpful in assessing our homes heating and cooling needs, offering options, and assisting in selecting a system that best matched the requirements at a reasonable cost. Jim was very detailed with explaining the differences in models and more importantly his installation plan. My understanding is the installation is just as important as selecting the brand and model! Jim and his team exceeded expectations and I would highly recommend!!

Jeanne Schroeder

23:29 01 Oct 25

I called Grenz Service Co. to my condo 4years ago to clean & get my natural gas fireplace working again. Jim G. was very thorough and even showed me how to relight pilot light if the flame went out again.Was so impressed with the professionalism that I had Grenz install a new furnace this Fall.Jim Jr and Conner worked so professionally. Put drop cloths down on my two flights of stairs up to loft and removed old 25 year old furnace and installed new Trane furnace in less than 6 hours. They had to work in a very small space and I was totally impressed!!!I will refer all my friends to Grenz Service Company because I am very happy with my new furnace!!!Thank you very much Jim Jr and Conner and Zack the electrician for a job well done!!!

Bud Reid

12:26 25 Sep 25

These people are the best at dealing with HVAC issues! Reliable, honest, prompt, & have solid knowledge of the trade. Plus charges are reasonable.

Ken Beckman

17:45 21 Sep 25

Price looks high, but included two furnaces and two electronic air purifiers. Spring service includes 2 air conditioners.

Matt Dawson

14:00 17 Sep 25

Great service and great guys. When a piece of equipment breaks down they are usually there pretty quickly and get the pizzas flowing again.

Diana Markus

19:14 09 Sep 25

Grenz Service Company gives us exemplary service! I have called upon them for several years and their team is prompt, efficient, and knowledgeable. I highly recommend. Mama Ds Coffee

Barbara Pinekenstein

22:05 07 Sep 25

Great customer serviceQuick response and always promptGood diagnostics and able to fix with a reasonable price

jethro boyd

20:57 05 Sep 25

Barb Christopherson

14:08 03 Sep 25

Kristine Seymour

01:40 21 Aug 25

Excellent customer service. Left the area pristine. Stayed late to get us air conditioning day 1 of a 2 day HVAC replacement. Good communicator.

Rohit Yajee

01:08 19 Aug 25

Very prompt and excellent service. I will recommend Grenz Services to anyone for Fireplace service. Jim took extra steps to ensure job well done. I am very impressed with the work and professionalism. Thank you, Jim and Grenz Service team!

Paul L

23:38 17 Aug 25

Jim was our technician and he was extremely fast! He figured out what was wrong with our AC unit almost immediately. He also had the parts on his van to get us up and running in no time at all. We are very satisfied and he is highly recommended.

Jeff Majinski

19:25 08 Aug 25

Prompt professional service. Trustworthy. Referred to company by a friend and now I will refer to others.

Cindy Schaefer- Padilla

18:56 06 Aug 25

We chose Grenz Service because of their high reviews and responsiveness to our initial requests. I am so glad that we found this business to install our AC and furnace. They were wonderful!

Jen Frank

15:35 04 Aug 25

Great experience and wonderful customer service. I would highly recommend Grenz Service Company.

RICHARD LESSNER

20:23 31 Jul 25

Jim is the best tech and I am not just saying that because he is my neighbor.

Lisa Perinovic

21:43 28 Jul 25

awrap Andringa

21:50 25 Jul 25

The boys were polite, and efficient. They explained what they were going to do and all that they did. Great job again.Thanks.

See all reviews Write a review

Debra T.

17:53 14 Apr 26

Grenz has serviced my AC, heating, and gas... fireplace for about 15 years.A wonderful family owned company, with old fashioned values of getting things done right the first time!read more

David M.

15:58 04 Apr 26

Grenz Service Company recently did two jobs at my... home.The first was installing a new HVAC system. Jim Grenz walked me through all the options and provided me with three quotes, each depending on the low, medium, or high grade HVAC that were recommended. They answered all my questions, did the install in one afternoon, and even entertained my questions and requests for system configuration tutorial. Awesome!The second was a repair to my gas fireplace. The pilot light had just aged, and my penchant for turning off the pilot after winter was not a good idea. Again, the service was excellent.I would highly recommend Grenz Service Company. Great products, great service, great prices.read more

Debra K.

21:10 01 Apr 26

We have used Grenz Service Company many times to... perform tuneup, cleaning of glass and burners and make certain all was working well with our fireplace. Recently had a pipe burst causing a water leak resulting in water to seep under fireplace unit. Grenz contacted me the same day I called and worked an appointment to come out to make certain all was working properly. During their inspection they even found and repaired a small gas leak. They are very professional, knowledgeable, kind, and work you into their schedule quickly. They know what they are doing and have always fixed anything we needed the first time. I highly recommend any of their services.read more

Judy B (Judy B.

00:45 30 Mar 26

We needed both central air and furnace unit. Jim... came out to our home to meet with us and provided a very thorough and comprehensive explanation of his products and services. He inspected our home and gave us several options. I have NEVER met an individual so thoroughly knowledgable about the industry, their product line, and technical details. Outstanding person to work with. Very professional communication - and timely! They reminded us of their upcoming visit and provided detailed receipts. (Nothing hand-drawn here!). The install was flawless - professional and hard-working team. I sincerely wish I experienced this degree of professionalism, honesty, and expertise with each company we worked with. We are very grateful we found Jim and his team. They are now our HVAC company and we would highly recommend them to everyone. Thank you Jim!read more

Leighann M.

00:50 27 Mar 26

Excellent customer service and always ensure done... right!Highly recommend.read more

Tee L.

13:11 25 Mar 26

Prompt, organized, efficient, fair price, good... communications.read more

James P.

17:34 19 Mar 26

Jim Grenz provides a service that nobody else in... this area does. He repaired our gas fireplace instead of us having to replace it.read more

Karli G

13:23 12 Mar 26

Jim Jr. was very pleasant to work with. He kept... me informed with what he was doing and explained things to me in a way I could understand. Very professional and personable.read more

gary B.

19:53 06 Mar 26

Great service. Was able to come as soon as he... could.read more

Chris C.

21:34 28 Feb 26

At this point, it looks like these folks saved me... between $1,500 and $19,000, depending on which of the suggested repairs/upgrades two other companies wanted me to agree to. Nice to have this company come give me a second opinion: “If it were my furnace, I wouldn’t do anything with it. It is running fine.” So, unless the furnace fails in the next some years, I’m grateful for this company’s assessment, which appears not to be self-serving.read more

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