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“SumZero folks did great work. Everyday they come and put down protection rag on the floors, and when they leave for a day they vacuum and clean up. So no interruption to our life while they were installing the heat pump system for us. The system has been working great, even in really cold weather, it heats up the house quickly. Best of all it have virtually no noise when it’s running. Great work!”

“We contracted with SumZero Energy Systems for a Heat Pump installation to our 140 year old home. Raphael came to our home and took the time needed to explain the equipment and installation process in full. He worked with us to facilitate the electrical upgrade required for the new system. The electrician worked with our City and electric utility to get us the complicated upgrade despite the equipment supply shortages. The installation coordinator, Jackson came out and walked around the house and discussed the location of vents, returns and mini-splits throughout our home, always listening to our concerns. We also went outside to locate the placement of the exterior equipment, again listening to our concerns. SumZero promised a two day installation for our complicated installation and they delivered. The installation crew was courteous and considerate during the whole process and left our property immaculate. The system was up and running by the end of the second day. In addition, our two old oil furnaces were removed. Our two oil tanks in the basement were also removed professionally with all hazardous waste handled by licensed personnel. The office staff was very helpful in the processing of the Heat Loan (0% financing) and the MassSave Rebate ($10,000). The Heat Loan was approved quickly keeping our installation date on track and the MassSave rebate was approved within 30 days of installation. We have enjoyed the comfort of full home air conditioning during the summer, not missing our AC window units at all. We look forward to heating our home this winter without burning oil.”

“SumZero is a wonderful company. From sales (Rafael) to administrative/scheduling (Michelle and Lara) to electrician (Chris) to installation (Fernando), everyone was professional, honest, thoughtful, and diligent. Communication is excellent. They put in a 5-zone system, took care of the Mass Save rebate for me automatically, and guided me through getting the Heat Loan (7 year zero interest loan). It took them 3 days to finish the installation and they made sure to always clean up before they leave. I am already looking to get more work done with them (adding recess lightings, ring cams, etc) because their pricing is very reasonable and their workers are personable/kind. I highly recommend SumZero if you are looking for to install a mini split system.”

“This is company is 5 stars all the way. From our first initial meeting, through scheduling, project managing and finally some of the best installers I have ever encountered. This company gets an A+ across the board. Excellent communicators, incredibly friendly and professional. Each step of the way, everyone and I mean everyone was top notch. They also have incredibly fair pricing. If you are looking for heat pumps, go no further, sum Zero is the best. Special thanks to Raphael, Jackson, Marcelo, Mark and Dennis! Okay, so this is 1 year later, 1st even though it was really cold last winter we still saved a few $$ for switching from oil. Most important, the air quality fron heat pumps is 100000000% better than oil. Feeling clean fresh air all winter while stuck inside too much was truly amazing. Just had our 1 year service call and sum zero continues to deliver. Professional and prompt with great communication. Great company I highly recommend making the switch if you are wondering.”

“Every single person we've dealt with from SumZero has been a model of professionalism and integrity. Raphael did a great job evaluating and helping us decide which heating system made sense for us (we replaced the old gas furnace and A/C with a new electric heat pump system). We felt no rush or pressure. Jackson did a great job with the walkthrough and answered lots more questions, again making sure we were confident before he left. The removal and installation was really well coordinated by Daniel, Wanderson and the gent who did the electric work. Everyone is very focused on doing right by the customer, down to even the smallest details. The team clearly takes pride in their work and their company. We also appreciate that SumZero has handled the paperwork needed for the rebates. Absolutely great job in every respect. Thank you SumZero, we look forward to continuing to work with you!”

“Had a mini-split system installed for both heating and cooling - did it as a part of mass-saves and had an electrical service upgrade at the same time. True professionals! Very responsive - had everything organized and anticipated my questions before I asked them. They were very respectful while in my home, and left it far better than when they entered. Would absolutely recommend them for anything HVAC or electrical related!”

“Making the switch from an oil burning furnace to a cold weather heat pump to replace both our heating system and aging air conditioner was tough research to do on my own. Most all heating and oil companies around here did their best to spread old misconceptions about heat pumps only working well in the south where the winters are warmer, but there were so many articles improvements and technology That I decided to reach out to a company that specialized in heat pumps. David and his staff over at SumZero in Holliston were both excellent resources for information and professional in their quick estimates and work. It’s by no means a quick process from beginning to end with all the great incentive programs and related in work requirements, but again this is where David and his team made everything so clear and easy. Since the installation, their customer service has remained excellent to both answer one off questions I had about heat pumps which definitely work very differently from oil and gas furnaces to follow up appointments for quick inspections and a backup add-on installation. We are two winters and one summer into the installation and everything has worked out splendidly so far! Especially given oil and gas prices around here nowadays we are saving so much money having switched over!”

“SumZero was able to replace our central air with an air source heat pump, reusing the blower from the existing furnace. This solution made for a very competitive option. They also helped with the MA Saves rebate application. Very professional 1-day installation! Highly recommend SumZero.”

“The entire SumZero experience was fantastic from start to finish. Paul came out and did a nice walkthrough to give us a full understanding of exactly how our system should be sized and quickly got us estimates with all MassSave included (and they take care of all of it so you get instant savings). Jackson and Lara were great to work with and did a great job with the project walkthrough and getting everything scheduled quickly. The team uses a nifty app called ServiceTitan so you always know who is coming and get live updates on their arrival which is extremely convenient. When the team showed up for the installation, they had everything they needed and were great about communicating every step along the way and asking questions to make sure everything was just how we wanted it. The attention to detail for the install was top notch (see pictures), and we are really happy with their recommendation to use a Bosch heat pump and Trane furnace. This gives us dual fuel heat that automatically switches depending on the temperature outside to get the best efficiency and we can keep an eye on gas and electric prices to manually switch if rates spike. We also got an ERV to improve indoor air quality, it is still early but I think this will be a nice upgrade to the comfort of our home. Can’t wait to see how the Bosch does in the summer heat. All in all, the SumZero experience was smooth and every single person on the team was great to work with. Highly recommended!!”

“We used Sumzero to replace our existing AC with a heat pump system. I was very impressed from my first interaction and found them to be extremely professional (extremely neat and tidy installation, covered all work areas and path throughout the house, wore foot coverings during the quote) throughout the process including their help with applying to MassSave for rebates. The new system functions very well and we are extremely glad we used Sumzero. I can’t recommend them enough - Five stars all around.”

“Working with Paul and his team was excellent start to finish. Very professional and responsive. Got 3 heat pumps and they took care of the $10k mass save rebate too. Love it.”

“SumZero folks did great work. Everyday they come and put down protection rag on the floors, and when they leave for a day they vacuum and clean up. So no interruption to our life while they were installing the heat pump system for us. The system has been working great, even in really cold weather, it heats up the house quickly. Best of all it have virtually no noise when it’s running. Great work!”

“We contracted with SumZero Energy Systems for a Heat Pump installation to our 140 year old home. Raphael came to our home and took the time needed to explain the equipment and installation process in full. He worked with us to facilitate the electrical upgrade required for the new system. The electrician worked with our City and electric utility to get us the complicated upgrade despite the equipment supply shortages. The installation coordinator, Jackson came out and walked around the house and discussed the location of vents, returns and mini-splits throughout our home, always listening to our concerns. We also went outside to locate the placement of the exterior equipment, again listening to our concerns. SumZero promised a two day installation for our complicated installation and they delivered. The installation crew was courteous and considerate during the whole process and left our property immaculate. The system was up and running by the end of the second day. In addition, our two old oil furnaces were removed. Our two oil tanks in the basement were also removed professionally with all hazardous waste handled by licensed personnel. The office staff was very helpful in the processing of the Heat Loan (0% financing) and the MassSave Rebate ($10,000). The Heat Loan was approved quickly keeping our installation date on track and the MassSave rebate was approved within 30 days of installation. We have enjoyed the comfort of full home air conditioning during the summer, not missing our AC window units at all. We look forward to heating our home this winter without burning oil.”

“SumZero is a wonderful company. From sales (Rafael) to administrative/scheduling (Michelle and Lara) to electrician (Chris) to installation (Fernando), everyone was professional, honest, thoughtful, and diligent. Communication is excellent. They put in a 5-zone system, took care of the Mass Save rebate for me automatically, and guided me through getting the Heat Loan (7 year zero interest loan). It took them 3 days to finish the installation and they made sure to always clean up before they leave. I am already looking to get more work done with them (adding recess lightings, ring cams, etc) because their pricing is very reasonable and their workers are personable/kind. I highly recommend SumZero if you are looking for to install a mini split system.”

“This is company is 5 stars all the way. From our first initial meeting, through scheduling, project managing and finally some of the best installers I have ever encountered. This company gets an A+ across the board. Excellent communicators, incredibly friendly and professional. Each step of the way, everyone and I mean everyone was top notch. They also have incredibly fair pricing. If you are looking for heat pumps, go no further, sum Zero is the best. Special thanks to Raphael, Jackson, Marcelo, Mark and Dennis! Okay, so this is 1 year later, 1st even though it was really cold last winter we still saved a few $$ for switching from oil. Most important, the air quality fron heat pumps is 100000000% better than oil. Feeling clean fresh air all winter while stuck inside too much was truly amazing. Just had our 1 year service call and sum zero continues to deliver. Professional and prompt with great communication. Great company I highly recommend making the switch if you are wondering.”

“Every single person we've dealt with from SumZero has been a model of professionalism and integrity. Raphael did a great job evaluating and helping us decide which heating system made sense for us (we replaced the old gas furnace and A/C with a new electric heat pump system). We felt no rush or pressure. Jackson did a great job with the walkthrough and answered lots more questions, again making sure we were confident before he left. The removal and installation was really well coordinated by Daniel, Wanderson and the gent who did the electric work. Everyone is very focused on doing right by the customer, down to even the smallest details. The team clearly takes pride in their work and their company. We also appreciate that SumZero has handled the paperwork needed for the rebates. Absolutely great job in every respect. Thank you SumZero, we look forward to continuing to work with you!”

“Had a mini-split system installed for both heating and cooling - did it as a part of mass-saves and had an electrical service upgrade at the same time. True professionals! Very responsive - had everything organized and anticipated my questions before I asked them. They were very respectful while in my home, and left it far better than when they entered. Would absolutely recommend them for anything HVAC or electrical related!”

“Making the switch from an oil burning furnace to a cold weather heat pump to replace both our heating system and aging air conditioner was tough research to do on my own. Most all heating and oil companies around here did their best to spread old misconceptions about heat pumps only working well in the south where the winters are warmer, but there were so many articles improvements and technology That I decided to reach out to a company that specialized in heat pumps. David and his staff over at SumZero in Holliston were both excellent resources for information and professional in their quick estimates and work. It’s by no means a quick process from beginning to end with all the great incentive programs and related in work requirements, but again this is where David and his team made everything so clear and easy. Since the installation, their customer service has remained excellent to both answer one off questions I had about heat pumps which definitely work very differently from oil and gas furnaces to follow up appointments for quick inspections and a backup add-on installation. We are two winters and one summer into the installation and everything has worked out splendidly so far! Especially given oil and gas prices around here nowadays we are saving so much money having switched over!”

“SumZero was able to replace our central air with an air source heat pump, reusing the blower from the existing furnace. This solution made for a very competitive option. They also helped with the MA Saves rebate application. Very professional 1-day installation! Highly recommend SumZero.”

“The entire SumZero experience was fantastic from start to finish. Paul came out and did a nice walkthrough to give us a full understanding of exactly how our system should be sized and quickly got us estimates with all MassSave included (and they take care of all of it so you get instant savings). Jackson and Lara were great to work with and did a great job with the project walkthrough and getting everything scheduled quickly. The team uses a nifty app called ServiceTitan so you always know who is coming and get live updates on their arrival which is extremely convenient. When the team showed up for the installation, they had everything they needed and were great about communicating every step along the way and asking questions to make sure everything was just how we wanted it. The attention to detail for the install was top notch (see pictures), and we are really happy with their recommendation to use a Bosch heat pump and Trane furnace. This gives us dual fuel heat that automatically switches depending on the temperature outside to get the best efficiency and we can keep an eye on gas and electric prices to manually switch if rates spike. We also got an ERV to improve indoor air quality, it is still early but I think this will be a nice upgrade to the comfort of our home. Can’t wait to see how the Bosch does in the summer heat. All in all, the SumZero experience was smooth and every single person on the team was great to work with. Highly recommended!!”

“We used Sumzero to replace our existing AC with a heat pump system. I was very impressed from my first interaction and found them to be extremely professional (extremely neat and tidy installation, covered all work areas and path throughout the house, wore foot coverings during the quote) throughout the process including their help with applying to MassSave for rebates. The new system functions very well and we are extremely glad we used Sumzero. I can’t recommend them enough - Five stars all around.”

“Working with Paul and his team was excellent start to finish. Very professional and responsive. Got 3 heat pumps and they took care of the $10k mass save rebate too. Love it.”