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

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.

Fast response - diagnostic appointment of AC unit scheduled for early next morning…read more Tech Kayla diagnosed problem quickly and explained options for fixing the AC unit quickly and clearly. Refrigerant was gone indicating it had one or more leaks. I decided to have the refrigerant refilled as stop-gap measure. The total cost for the appointment was $517. It was a failure on my end to not ask if I could have gone with less refrigerant to save money. In the end I'm only using the AC unit for 14 days before having it replaced. Kayla's estimate for repair was approximately $5000 plus a chance for it to be more based on the time it would take to find the leak(s). I decided to go with replacement of the AC unit based on its 11 year age and the approximate cost of $6000 to fix it. Sales person Steve contacted me later that day and scheduled an appointment to get an estimate for replacement. I found him personable and professional and he gave his estimate promptly with the information I needed about it. I had 2 followup questions that he quickly answered. In the end I went someone else for the AC unit replacement, but more because of an option to include switching my furnace to have an electrostatic filter at the same time I did the AC unit replacement. The cost of the AC units were similar. Overall very good diagnostic and fix, as well as quick followup on providing an estimate for replacement.

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

I was told the service visit would be $125. I was then charged an additional $175 for about 45…read moreminutes of the technician's time, for a total of $300. No repairs were performed and I was ultimately told that the AC was operating normally, without a solution to the temperature difference I had called about. I understand paying for diagnostic time, but $300 for this visit felt very expensive, and I wish the additional charges had been clearer when I scheduled. Update: I appreciate the business owner commenting on their charge process. The technician specifically noted charging me for 45 minutes, and I have an email time stamped 45 minutes after he started work. Also, none of the paperwork notes that the initial charge includes 30 minutes of time, which further emphasizes my point about transparency. Update: Update: I previously listed the wrong dollar amounts, so I am correcting them after reviewing my invoice. I was charged $149 for the diagnostic visit plus $130 for an additional 45 minutes of labor, for a total of $292.95 with tax. After the business stated that the technician spent approximately 75 minutes diagnosing my AC, I requested their timestamped records. Their records show that at 12:38 PM I signed their Customer Acknowledgement stating that "all work has been completed," and my invoice was emailed at 12:40 PM. However, they are counting time through 12:51 PM toward the 75-minute visit based on their tracking system. I disputed the additional labor charge and requested a refund. The company refused and offered only a credit toward future service, which I declined. My concern is not that diagnostic work costs money. My concern is being charged for diagnostic labor that I do not believe is supported by the company's own records.

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!

Very inconsiderate people. They run a business like authoritarians,what they decide is it. Recently…read morehad my proppane an pulled because I did not buy enough fuel, even though I paid yearly tank rent . He offered to put in 100lb bottle for $85 a tank, which is about 1/12 times the propane cost, and would have cost me just about double filling the 100 gallon. I wrote them a letter and explained that along with the hassle of restarting furnace when tank goes empty, also explained I have done all my business with them and the gas station for 26 yrs. Seems no difference or loss to them at all as never even had a call to negotiate an alternative to what he presented me. Not the most people freindly even at the office with the secretary, they make you feel like you are stupid and they know better. Thanks and would never recommend doing business with them. Val Kitzan

The owner Larry William is dishonest and underhanded when it comes to his business practices. He…read moreovercharges customers and then actually wants payment to pump fuel from the tank. He has the audacity to charge $7.54 to pump the said gas. He then compensates the owner with a mere 52 cents per gallon and charges the owner $2.11 per gallon for the fuel. Only under great duress did he forego the tank emptying charge. I would never do business with this company again and I'm disappointed that a small local business has no integrity.