SumZero Energy Systems

Heat pumps are the whole pitch at SumZero Energy Systems, a Holliston company that calls itself a heat pump and electrification specialist and says it handles the Mass Save Heat Loan and rebate paperwork for its customers. It holds 4.9 stars from 501 ratings on Google and an A+ from BBB, and a 2026 Reddit commenter put it among the high priced options. The installs customers describe are sizable. A July 2026 Google reviewer had seven mini splits put into a new home and said the team helped with the rebates. In an April 2026 review, a homeowner said the company put in a 5-zone system and that communication was excellent. A March 2026 customer had mini-splits and an electric booster added to cut their reliance on oil heat, and said the company came back promptly for touch-ups and adjusted the scope and price when part of the original plan proved not feasible. A January 2026 Reddit commenter said a 2000sqft town house cost about 17k, down to 13k with rebates. The complaints center on what happens after. A February 2026 Google reviewer said their heat pump failed during the coldest stretch of winter and was still not fixed after a week. A September 2025 Angi customer said all three systems the company installed malfunctioned within the first year and that the company then stopped responding to emails. An April 2026 reviewer called the AC installation shoddy and said support a few years later was close to none. A June 2026 3-star review praised the technician but said an outlet SumZero installed failed, so the sump pump did not run and water overflowed onto the basement. A March 2026 reviewer never received an estimate after a consultation, though the sales agent later apologized. Its Massachusetts HVAC license is active.