UPDATE: A few hours after writing this we LOST ALL HEAT DURING A BLIZZARD. No power interruptions, it is THE SYSTEM NOT WORKING YET AGAIN. Called only to be told we'd get NO help or support for two days. Our entire house is only around 55 degrees now and we can't safely leave. DO NOT USE THIS COMPANY. I am so unbelievably upset. We called Friday asking for help and now here we are, heatless with two kids home during a blizzard. ----------------------------------- I waited a long time to write this review because we gave SumZero many opportunities to correct ongoing issues that have existed since day one of installation (a few years back). Unfortunately, we continue to have persistent problems with both heating and cooling. We have two young kids and at this point it is unacceptable these issues haven't been resolved. In the summer, our back room with vaulted ceilings is consistently 5+ degrees warmer than the rest of the house. In the winter, that same room is always about 5 degrees colder. The main living areas also had issues for the first few years, struggling to maintain temperature in the summer and leaving the house humid and unable to hold the thermostat setting some days. After extensive back-and-forth, SumZero ultimately replaced the entire outdoor unit, stating we must have received a "lemon." That replacement was installed this past summer, yet the temperature imbalance in our back living room remains unchanged this winter. Separately, we were provided a mini-split for our partial basement living room. That unit is unreliable and often does not work at night. The settings are correct, we have tried power cycling and resetting the breaker, and it still works only intermittently. It has been set to 68°F for days, yet the room is currently 56°F with no warm air blowing, despite the unit being on. My husband and I have contacted SumZero countless times over multiple seasons and years. Even after replacing major equipment, we still do not have a system that can adequately heat and cool our home as promised. The heat pump system installed through MassSave has never performed adequately in the years since installation. I understand that some older heat pumps can struggle in extreme conditions, but high-efficiency systems (like one we should have received via MassSave rebate with SumZero) should be able to handle New England winters and hot, humid summers., from my research. Ours cannot do either consistently. At this point, we are exhausted from having to address these issues every few months. While the customer service representatives and technicians are polite, no one has been able to properly fix the system. I strongly recommend going with another company if you want to avoid a long-term headache. Photos show mini split remote temp set to 68 but room thermostat shows 56, this is a common occurrence. Other photo shows main house ecobee (new thermostat for heat pump unit) set to 70 (has been set to this for months) but it's only at 65 in reality and continues to go down. The back room with vaulted ceilings thermostat currently reads 59 even though it should be at 70. read more

Great company! Honest people and fair prices. If you're anything like me, you hate shoddy work, and in the home remodeling industry, there's a lot of that. I would rather pay a premium to ensure it is done right and the quality is there. SumZero does that and more. We called, and within a day, they sent one of their experts, Raphael G., to quote us for ductless mini-splits to outfit our home. He was very thorough, offering different options that would work for our living room and bedrooms, which are boiling and humid during the summertime. He made the process extremely easy for us to understand and was willing to work directly with our condo association to accommodate their requests. We're still waiting to get them approved by our condo association, as there is a lot of work involved in obtaining approval. However, so far, the experience has been nothing but easy and painless. I'm looking forward to having the mini-splits installed. read more

I contacted SumZero to provide a quote for a new HVAC system. From the first phone call, I was impressed by the professionalism of the company. Paul came out to my house and spent ample time explaining the process and educating me on the basics of system sizing and functionality. He was polite, friendly, and answered all of my questions. What really made an impression on me was that he pointed out our hot water heater was not venting to code (unlined masonry flue). I truly appreciate that he noted this, since it led me to do more research and ultimately discover that this safety issue had been overlooked by three other contractors who had previously worked at our house. He really went above and beyond, and I appreciate his honesty and concern for safety, even for things outside the scope of his work. It says a lot about him and the company. read more

Marley Junio & his crew did a great job installing a minisplit on 8/26. Very professional and worked efficiently. They were on time, kept my house cleaned and kept me informed of everything. read more

I called one of the large area companies who run a lot of TV ads to come out to service my A/C, heat pump and furnace. September was the earliest they could get out. 5 months. You gotta be kidding me. Called Sum Zero, what a difference. Arranged for a tech to come out within 4 days. Arrived on time, very professional tech (Neilson), explained everything and left with a delighted customer. Raving fan. From the office staff to the techs, Sum Zero outstrip the bigger name companies. Highly recommend Sum Zero. Great locally owned and operated company. read more

We had a great experience with SumZero installing 6 minisplits and 2 condensers. Long story short, we initially went with a different HVAC company (never having met with SumZero), and that company strung us along for months (partly due to genuine supply chain issues). When installation day finally came they showed up and said they couldn't do the job. So back to the drawing board. We then met with 7 or 8 HVAC installers, most of whom we hadn't met with before. SumZero's quote was middle of the pack. Unlike everyone else who was fine maxing out the minisplit BTUs, SumZero very much cautioned against oversizing the units and now that I've learned more about these technologies I really appreciate their working to size the system correctly. They also split up our two zones in a smarter way than anyone else was proposing. The SumZero team that came on install day were among the nicest contractors we've worked with on any of our various house issues we've had. After install we were having a smell issue with a couple of our units. Our SumZero contact came by to check on the issue, and I so appreciated how he didn't try to gaslight me. The smell wasn't happening at first when he arrived and instead of saying "Well ok, I guess there's no issue!" he stuck around and seemed genuinely curious and motivated to figure out what was going on. He did eventually smell it. They sent their techs out promptly after that and discovered there was something that wasn't wired correctly that was causing units to fire at the wrong times which caused excess condensation, and they fixed it. For what it's worth, we discovered after picking SumZero's quote that some friends of ours used them and also had a good experience. read more

... watching contractors work on your house did you ever think- "wow these folks sure work like they work on their own homes?".... No? Sarcastic much? Wishful thinking? I thought so too. We all dread dealing with contractors as we know most of them are.... Dreadful to deal with. Facts. So that is how I felt too when I decided to switch my house from oil heat to electric. Due to the size of the house It was going to be a large project involving a complex setup of multiple condensers, air handlers and ceiling cassettes. I had in mind what I wanted, so I needed a contractor to look at my design and make changes as needed, provide input based on experience and execute it. The vendor would need to understand modern cold weather heat pump solutions and installations in a complex near- commercial environment. They also would need to understand integration with the heavily automated existing controls in my house. Like a good citizen I solicited several well- established HVAC vendors to provide me with quotes. I actually spent an hour or more with each one showing and explaining my property and current set up. All nine of the contractors said they can do it and will provide quotes. I got back... 3 quotes. But it wasn't a problem as I knew which vendor I will go with based on my interactions with them price notwithstanding. Ilija from Sumzero was the only guy that was technical enough and had sufficient knowledge to understand what the project involved and to make welcome changes to the specs and equipment based on load calculations. The installation went as planned. The team led by Paul showed up on time every day and worked extra hours to finish the job in a week. Remember the opening statement about contractors working like they work on their own home... This was how it looked and felt when I watched them work. No corners were cut and when I asked for a bit more here and there I was accommodated without any questions. Marcelo (lead tech) and the team worked hard and provided outstanding results. The last day presented a challenge where my existing controls needed to be integrated with the new controls. Daniel is their controls guy and our initial conversation was actually funny. I started to explain how I want the integration to work and Daniel interrupted me midway and finished my thoughts. Yeah- he is that good. Overall, I believe that companies like Sumzero are very very rare in the field. Knowledge, expertise, work ethics, communications with customer- it is all done well. So if you have an HVAC project regardless of its complexity- you should give them a call. You will not be disappointed. My 2 cents read more

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Great service, great planning and installation. Superb team of technicians who kept us informed throughout the process. We are 100% satisfied. read more

Loved working with David Sampaio and SumZero Energy! I had gotten multiple quotes to install central AC and David from SumZero was by far the best!!! - Extremely reasonably priced - Uses high quality equipment (Trane) and provides options (explains the difference in Seer 13 vs. 16 and broke out cost/benefit analysis for me). All of my other quotes from competitors using Goodman Seer 13/14, which is not as high quality as Trane. - Was extremely kind and patient in explaining the options - Incredibly professional and organized (excellent communication, installed our central AC in 1 day!) - Included warranty and other details - Went above and beyond reinforcing insulation on our HVAC - Immaculate work - Crew was fantastic and left our property spotless after they left David and SumZero was by far the best. David and his team has a phenomenal work ethic - from frequent communications (i.e., texting us he was running a bit late for our consult, breaking out $ savings) to the crew cleaning up everything after they left. We never felt he talked down to us - he was incredibly polite and informative. His team did an absolutely beautiful job installing the central AC - the work is immaculate. It was an absolute pleasure to work for someone who clearly wants his business to have a flawless reputation. David provided lots of details regarding warranty and I have full confidence if we were to ever have an issue or HVAC question we could contact him. read more

My hot forced air furnace was not firing Up, so I called them up for replacing the furnace as it was rather old. The estimator came inspected the furnace, but he was not professional handling the customer asking nonrelevant questions not being focused on the subject matter. I've decided not to pursue having the Sumzero any further since their services was highly unprofessional right off the bat from the beginning handling the business. They need to train their employee how to treat the customers well. read more

Excellent service and speed. Fair pricing, they help with the rebates from the state, they all wore masks and were respectful during COVID-19. I honestly felt like they were treating my house like their own! We had a split head pump unit installed for our bedroom / work area . Its been 3 months now and no problems, they unit is exactly as they described it. There were more expensive units, we chose a middle of the road price point, there was NO pressure to move to the better / more expensive model. read more

Was looking for heat pump mini splits installed in my house. Paul Jameson came in to give free estimate. He turned out to be very incompetent: didn't know basic MA building codes - proposed outdoor line going over my electric main. Included most powerful condenser in his estimate for 3 small rooms, when asked how he came up with this BTU numbers and why it needed, stopped replying my emails. This was about month ago, haven't heard from them since. They have good reviews, that why I called them. Not recommended! read more

Ilija and the crew from SumZero did an excellent job with a gas heater install for my garage. Their bid came is substantially lower than others, which made me concerned about the quality; I took the chance and I'm glad I did. The bid was done very quickly and the project install took place 3-4 days later. It took about 1/2 day and was done flawlessly. I'll be sure to use SumZero on any future HVAC projects I have. read more

We were having some issues with our whole house air conditioner. I went to our A/C's manufacturer's site to find a local service contractor and it said Sum Zero Energy could service our system. I called SumZero and asked the woman who answered the phone if they did service. I told her the make of the unit and she said they do work with that manufacturer. She said that's all she knew and could not answer any other questions, but rather another woman would get back as soon as she was out of a meeting. Never heard back from them. read more

Working with David on replacing my dead 20-yr-old gas furnace, and working but similarly-aged AC was productive. Took a bit of work agreeing to what exactly needed to be done but, eventually, the installation was smooth and nicely done. And fairly priced too. David and Ilija seem like a bunch of young and energetic owners, very capable of handling relatively straightforward jobs like full replacements. The entire job was completed in one day. Hopefully nothing else will break in my house but, if it does, SumZero will be the first company I'll reach out to. read more

We had minisplits installed in our third floor condo and had a great experience. The estimate process was fast, clear, and thorough. They were able to get the project on the schedule within a few weeks. Their entire crew was amazing. They were quick, clean, and friendly. They were also incredibly patient with my fellow condo owners making changes to the plan and pivoting easily. read more

After a long and arduous search for a quality company to install a new multi zone mini split for my home, and finally narrowing it down to three, I decided to go with Sum Zero, and I'm glad I did. While I really liked the other two companies as well, there were countless little things that made a big difference that Sum Zero did for me. The communication was flawless, everyone I worked with was very helpful, and the attention to detail was impeccable. The installers did an amazing job, and I'm particularly thankful for their incredible hard work. I would recommend Sum Zero without reservation. read more

This was a completely, 100% professional experience. David Sampaio was super responsive on email right from the start and came out to the house to give me a quote. He also gave me some other recommendations on unrelated energy savings. When the crew came out for the install (central air on the first floor, mini-splits installed in the two bedrooms on the second floor) the guys were super nice and super professional. My wife was home for most of it so she dealt with them and they treated her with the same deference and respect they treated me. They explained everything very clearly and asked for our input on where we wanted things. They also wore shoe nets when they were in the house, which was nice of them. It was supposed to take three days, but they were actually able to get it finished in only two! We are very happy and would 100% recommend them to anyone else who is looking at having any HVAC work done. read more

Paul and his crew did an amazing job on our heating system. When it was not exactly what we had agreed upon after installation, he had his team return and make the adjustments. The next day. Fast and at no charge. He provided quick, friendly and helpful service in an industry not know for timely quality. Thanks to Paul and the guys for a job well done. read more

Illija and his crew installed a mini-split AC system for my small house. They were vastly less expensive than three other quotes, yet did top quality work. They were very professional and respectful of COVID constraints, and arrived exactly when they said they would (which was a great sign for how they were going to handle the install). I rarely post reviews, but when a small company does such outstanding work for such a great price, I feel compelled to let others know. read more

These great folks installed spray-in foam insulation and a Mitsubishi multi-split system for our 1,000 sq. ft. in-law suite addition. Lots of design complexities and challenges but they were on top of it all and wonderful about explaining things and coordinating work with others on site. We've now seen the results for both cooling and heating weather and all's working wonderfully. We recommend them highly. Thanks Ilija and co-workers! read more