I just really appreciated what seems like an honest assessment. I was looking for a second opinion,…read morebecause two other companies had recommended major, costly repairs or replacement for my gas furnace. The Grenz folks came, carefully looked at the unit, and said, "If it were my furnace, I wouldn't do anything. It is running the way it's supposed to." This second opinion cost me something, naturally, but it also saved me between $5,500 and $19,500 (two quotes from the other two companies). Jim seems like a straight shooter. I'd recommend you give these folks a try.

He called me back and talked me through the fix. He did not wait to come out and wouldn't take any…read morepayment for his assistance. He clearly knew what he was doing. He was able to talk me through several troubleshooting exercises without seeing the gas fireplace itself. If I have any HVAC or fireplace needs in the future, I will definitely use Grenz

Tom misquoted work I hired him to do. He gave me a quote, showed up for the job, realized he didnt…read morepay enough attention (he overlooked my basement ceiling being drywalled ) He started the job but decided after cutting three vents holes in my floors that he didn't want to finish the job he misquoted. Than he sent Elizabeth his admin person to do his lying for him. They now demand i remove the entire ceiling and verify there is no mold or asbestos before they will return. We discussed the condition of the basement, specifically that there is soke mold and likely asbestos wrapped pipes. The morning he arrived to do the job he immediatelyadmitted he screwed up. He assured me he would do the work anyways as it was his mistake. Now he won't respond to messages sent directly to him, and Elisabeth is like dealing with a child who will not admit they are wrong. Despite the very good reviews, it has been a nightmare trying to get this company to follow through with what they said they would do. I strongly recommend you look elsewhere for your work.

Tom Yodor maintains the HVAC equipment in my home. He does a terrific job, and is very…read moreinformative so that I can plan work in the future. This past Monday he installed a new Honeywell T10 Lyric thermostat. He tied this in to my existing bypass humidifier to automatically control it to minimize window sweating in the summer. The new controls required a new wire to tie the thermostat to the humidifier. Tom efficiently ran the wire from the main floor to the basement. The T10 can also control via remote sensors to assure adequate heating and cooling. I am very happy with the thermostat, and how the system operates!

Very knowledgeable serviceman who answered all of our questions. Very professional yet with a…read morepersonal touch. Was truly interested in our specific concerns and questions. Did not take long to arrange an appointment. Offered suggestions on best way to set and regulate our furnace. After many years with another company that we've learned to distrust, a change was necessary and Donovan & Jorgensen definitely left us with a very good impression.

Just wanted a ballpark quote on my boiler that's working but acting up. To start they demand info…read morelike address and a phone number straight out the gate, I'm sure it's so they can harass me later with "do you still need" calls a week from now and when you give it you find out they charge $100 just for a diagnosis. Don't waist your time They clearly don't want the business.

Two ambitious projects in the past year: 2 new replacement boilers and 2 new air conditioning…read moresystems. All four were professionally installed, at budget, and on time. The high pressure A/C is unobtrusive, and the new heating takes up maybe 20% of the old system. Special shout out to Brian, Larry, Carl, and Tim. Quite a crew.

From the owner: We are your number one source for Comfortmaker heating and cooling products. We provide the best…read moreprices on the best products for residential and commercial furnaces, heat pumps, boilers, and air conditioners. We also service all makes and models.

Thielmann: I'll try to give a brief background. The furnace (unit also has AC component) in my…read morecondo was having white smoke/steam come out of the external vent during some of the extremely cold weather we were having. Even though my furnace was not making any unusual noises, smells, or setting off my carbon monoxide detector, I was still concerned as no other condos in my building or nearby buildings were having the smoke/steam. The employee that initially inspected by furnace (Carlos?) informed me that the heat exchange was clogged and would require me to repair the furnace or purchase a whole new unit (I opted for a whole new unit based on its age). Carlos gave me the impression there was no rush and that it was not something that necessarily needed to be done immediately. When the second employee (Dave?) came later that day to take measurements and verify the replacement unit needed, he made it seem almost emergent and began to wonder aloud if he needed to shut my furnace off that day. The stark contrast between the two was alarming and created a bit of a trust issue on who to believe. Carlos seemed a little green and Dave seemed like more of a veteran. Dave eventually determined it did not need to be shut off as no carbon monoxide was entering my condo. The whole experience did create a bit of a panic for me though, so I quickly accepted the only available appointment within the following two weeks. It was convenient that they could get it replaced just five days later, but if it truly wasn't an emergency then I would have liked a little more time to verify I was getting the best price as it wasn't cheap (to give you an idea this is the largest purchase I've ever made behind my home, education, and car). They do offer payment plans that were easy to enroll in, one of which has 0% interest if paid off within a year. I'm not trying to throw anyone under the bus, but I can tell they really want an honest review as I've received multiple texts and emails asking to leave one. The crew that showed up on the morning of 12/24 to install the new unit were quick and efficient. They were respectful of my property and explained the new thermostat to me. All the employees were friendly, including the ones running the office over the phone (Micah?).

Thanks to the flooding my hot water heater is shot! I called Thielmann (since they previously were…read moreRoss and that was the service I use to use) they came out to inspect my pilot light situation and unfortunately just the inch of water I had is the right amount needed to short circuit things. He also made sure to check out my furnace to ensure there weren't any issues with that - I knew the AC was working fine but he ran a service check on the heat as well. I am a little confused as to what's happening for the next appointment I've set up - is this to gain an estimate on a new heater or to actually install one which is the reasoning for 3 versus 4 star. Tried calling back to find out but couldn't get ahold of someone. I'd like to get a few quotes of course for something like that/have a discussion about the types of options for water heaters.

Last winter the furnace in my rental house quit working, I called them and he diagnosed the…read moreproblem, went to Waukesha for parts, returned and promptly restored the heat. Five at-a-boys for them !!!

This company displays professionalism, expertise and excellent service. Both TJ and Mike are very…read morehonest, reliable, and timely. They leave you with the feeling like you were their only customer. TJ's dad installed our heating and air conditioner 20 years ago with a young TJ by his side ;) It is so cool to see the same business practices in play, to make customers want to keep coming back! Keep up the good work guys! I highly recommend this company.

I have had 3 good visits from this company over the last year and a half. Last night Matt the owner…read morecame out and diagnosed an issue that was causing our heat to shut off on the coldest day of the year. I thought there was no way I would get anyone out on a holiday and freezing cold day. He made it out late In the afternoon and called me and told me me that he was not going to charge me because he thought maybe they could have caught the issue at our yearly check. He was so incredibly professional, and above and beyond helpful and kind. I went from starting the day feeling like we might have big issues on worst possible day, to having the most pleasant call confirming it was fixed at no charge and they appreciate our ongoing business. A truly great business and owner !

These 2 guys are the best! They're honest, they save u money every where that they can, but still…read moregive you better service than I've ever seen with any other business, PERIOD!! You will not be disappointed in any way with Matt & Mitch. They're honestly too good to be true! I can't believe that I'm this excited over hearing & A/C, but that is what a breath of fresh air these two are when you're going thru something not pleasant, like replacing your furnace!

We had a new furnace installed in 2023 and a new air conditioner in 2024. We signed up for the…read moreannual "Maintenance Agreement". Well, we are 100% satisfied with the quality of workmanship, professionalism, prompt service, friendly attitude and excellent products sold. We have never needed a service call on either machines to date. The annual maintenance is such an outstanding offer. It gives you peace of mind that your investment is being taken care of. I would love to recognize Ray Seeber, our technician for his outstanding quality of work. He was so informative, patient and respectful. Thank you Ray, we look forward to seeing you again. Kettle Moraine, you are certainly the BEST!!!! Mr.& Mrs. O'Brien

So pleased with the service I received from Damyon Selby at Kettle Morraine heating. He completed a…read moretune up on my furnace, was very knowledgeable and personable. He provided me with a description and cost of maintenance that will be needed in the future and I didn't feel like he was trying to sell me things I didn't need. I will absolutely request Damyon for our future furnace needs and will recommend him and Kettle Morraine heating to others.

They were recommended by a friend of mine, and they were both very inexpensive and prompt. They…read morereplaced my furnace and air conditioner, replaced the condenser outside and helped upgrade our ductwork. Mark is really nice and I trust him implicitly.

I had Mark's heating quote a project for me along with 5 other competitors. To start things off,…read morethe person that answered the call was helpful and thankful for the opportunity. Mark made himself available to my time so he could stop by and understand the project. His quote came back quickly and he was able to start work in a reasonable time. He always returned phone calls and was a true pleasure to work with. Mark's work quality is excellent AND his prices were the best I found! Excellent Job Marks Heating!