“You have to let people know that the technology exists.”
That’s one goal of Michael Garrabrant, founder and CEO of Stone Mountain Technologies Inc. (SMTI), which has been building momentum in residential and commercial heating for more than 15 years.
The Tennessee-based company is ramping up production of its line of Anesi gas heat pumps for homes and businesses across North America – this after increasing its involvement over the past several years by attending trade shows and talking to industry stakeholders on the residential and commercial side.
“You have to go out and beat the streets, get in front of contractors, specifying engineers, energy-efficiency advocates and regulators, and start the process of educating what this new technology is and what the benefits are and why they should be interested in it,” Garrabrant says.
▶ An engineer’s work
Garrabrant helped to refine the technology as an engineer from Ohio who immersed himself decades ago in the possibilities of ammonia water absorption technology. With gas absorption, the system is leveraging combustion heat to capture additional energy from the outdoor air.
The company took a big step in 2023 when it moved into a 160,000-sq.-ft. manufacturing facility in Piney Flats, in the northeastern part of Tennessee, where roughly 50 employees (in engineering, technical support and production) work to carry out its mission. After years of R&D and product development, SMTI is now producing an 80,000-Btu gas heat pump, its introductory product for residential and light commercial applications, with plans to scale up unit sizes.
“We believe we can build 75,000 heat pumps a year out of this facility as we continue to grow,” Garrabrant says. “So, it’s a great place to be.”
According to SMTI, the product is unique in that it’s built to thrive in cool and cold climates – in regions that experience at least 4,000 heating degree-days per year and where electric heat pumps struggle to perform.
In fact, the gas heat pumps, fueled by natural gas or propane, offer advantages over their electric counterparts in retrofits or new construction, SMTI says.
With the gas heat pump, homeowners can enjoy cost savings owing to a modern, efficient unit; they can feel a consistent, comfortable and reliable heat on cold days; and they can rest assured knowing their energy choice with propane is environmentally friendly.
“Taking a heating product from 92 percent to 95 percent efficiency is interesting, but it doesn’t move the needle much. But going from 95 percent to 140 percent is a game-changer,” Garrabrant says of the product’s AFUE rating.
▶ Propane’s perspective
SMTI’s gas absorption heat pumps are drawing the attention of propane industry leaders who are intrigued by how the technology can position LPG in its ongoing battle with electrical equipment.
In fact, the National Propane Gas Association (NPGA) shared information about the company and its heating technologies during the association’s 2025 fall board and committee meetings in Burlington, Vermont.
While the thermal process offers multiple advantages for customers, heat pump efficiency and performance are the focal points for NPGA officials.
NPGA cites the heat pumps’ AFUE rating of up to 140 percent and their coefficient of performance of 1.43. These ratings give SMTI gas heat pumps a significant advantage over other equipment currently on the market, including that of electricity, according to NPGA.
“When you hear ‘heat pump,’ automatically everybody thinks of electric, and that’s not necessarily the case. Some of the challenges of electric heat pumps are the strong suit of a gas heat pump,” adds Bert Warner, director of commercial business development for the Propane Education & Research Council, noting how the gas heat pumps can perform in any climate and at good efficiencies.
SMTI’s gas heat pump technology also proves versatile as it can be configured to fuel residential and commercial water heating applications as well, bringing added benefits amid the growing challenges of electricity.
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