• Q

  When saying that natural refrigerants are more efficient than HFOs, what conditions is that assumption based on? Is there a certain lift or water‑temperature scenario? CO₂ can get pretty inefficient at higher entering heating water temperatures, correct?

  This is a great question, and the nuance matters.

  It’s true that CO₂ can become less efficient when rejecting heat into the outdoor ambient on a hot day, so operating conditions play a major role. In general, natural refrigerants can be more efficient than HFOs, but the conditions vary by refrigerant. Ammonia tends to excel across a wide range of temperatures because it has a very high latent heat of vaporization, which means it requires a lower mass flow for a given heat load. Its thermodynamic properties also allow it to match or exceed the efficiency of many F‑gas solutions across a broad temperature range.

   

  Hydrocarbons show strong thermodynamic behavior as well, typically resulting in efficiencies comparable to or better than typical F‑gases. CO₂ becomes particularly efficient when the sink temperature has a high lift, in cooler ambient conditions, and in heat‑recovery scenarios.

   

  Because CO₂ has very high fluid density, it provides excellent heat‑transfer performance and is well‑suited to systems that combine high‑ and low‑grade heat recovery. It also performs very efficiently in cooler ambient temperatures, making it a strong fit for year‑round cooling loads rather than seasonal AC demand. Typical uses include potable hot‑water heating in a transcritical water cycle and applications with multiple layers of cooling and higher‑grade heat recovery.

   

   

• Q

  Do you have residential heat pumps? What is the lowest temperature for these?

  The capacities and design considerations in residential tend to be very small relative to our work, and the residential market often faces capacity drop‑off as temperatures fall.

  There are examples of ambient‑loop systems that connect to multiple residences in a neighborhood to a central thermal network, and that helps residential heat pumps operate efficiently, our role in this type of system has been to provide the central heat pump connected to the ambient loop, rather than providing the residential heat pump itself.

• Q

  With the carbon taxes removed, how can we justify pursuing low‑carbon heat‑pump technology given the potentially high capital cost?

  There are viable pathways. Incentives remain important, and identifying the most viable opportunities is critical—especially those that maximize COP and leverage heat reclaim.

  As a test case, we removed carbon tax from our internal heat‑pump calculator and evaluated a scenario for an Industrial Heat pump chiller replacing about 480,000 m³ of natural gas use (roughly 2,240 MBH). In that case, a 135‑ton heat pump with 247 HP compressor showed an 11‑year payback without incentives. With a maximum Enbridge incentive of about $250,000 plus other stackable incentives (e.g., an additional ~$150,000), the payback could be reduced to around seven years. More broadly, this underscores the need to target the best applications: lower lift generally yields higher COP and better economics.

  Rather than chasing high‑lift, air‑source cases with marginal COP, it can be more effective to focus on heat‑recovery heat pumps—pulling from existing processes where possible—and on lower required outlet temperatures (e.g., 110°F rather than 140°F) to simplify staging and improve COP. Other drivers for decarbonization include municipal & state level decarbonization policies that still exist in many locations in North America.

• Q

  Can a heat pump work without supplemental heating when the source temperature is very low? If not, won’t we still face GHG emissions from supplemental sources?

  In industrial applications, it can be done if the use case is chosen carefully. As a reference point from our internal example, using readily available components, an air‑source ammonia system can be arranged for industrial space heating. With outdoor air at approximately −35°F (about −37°C) and indoor air around 90°F, the system concept produced a heating COP of about 2.9 (and about 1.9 on the cooling side). At 0°F outdoor, the heating COP would be around 3.9. These efficiencies reflect low heat‑recovery temperatures; if the target is 140°F–160°F, COP drops significantly. Also note that the simple example above did not include any losses from defrost cycles, which will reduce net COP in freezing conditions. The key is to match the application—e.g., industrial spaces that only need moderate indoor temperatures (around 50°F) can be heated efficiently even from very low outdoor air, whereas high‑temperature hot‑water requirements impose a steep efficiency penalty. A completely decarbonized district heating system would also deploy thermal storage and electric boilers, this provides the maximum flexibility to optimize the overall system performance.

• Q

  It appears propane heat pumps are gaining traction in Europe.

  Acknowledged. Europe is ahead of North America in the deployment of heat pumps, including natural‑refrigerant systems.

• Q

  You showed very small payback periods. I assume these depend on the cost of gas and electricity—are they still realistic?

  Yes—payback depends on gas and electricity prices, as well as available incentives. The specific short payback examples referenced came from feasibility studies in industrial settings and utilized waste heat, which raises COP, increases savings, and shortens payback. Those examples were from industries like wineries and breweries and were based on recovering waste heat and boosting its temperature. That drives higher COP and greater energy savings, which shortens payback.

  In jurisdictions where the current spark gap already favors electrification, these cases can be viable; still, each project’s economics are site-specific

• Q

  Are there air‑source heat pumps that can operate at 100% of capacity at −20°C (or lower) and still deliver a COP of ~2? Are such units commercially available?

  All refrigerant‑circuit heat pumps experience capacity drop as outdoor temperature falls, so maintaining full nameplate capacity at very low ambient is generally unrealistic. It’s important to size the heat pump for the required load at the minimum design temperature. 

  Regarding COP ≈ 2 at −20°C: yes, this is achievable, but it depends on the heat sink temperature. For industrial heat pumps, a heating COP of 2 at −20°C is readily attainable with appropriate sink conditions; achieving this with off‑the‑shelf commercial products can be more challenging.

• Q

  Are there packaged air‑to‑water heat pump solutions that integrate well with existing heating plants?

   

  Commercial packaged options are currently more challenging and limited. For industrial applications, there are viable made‑to‑order or integrated solutions, and we routinely engineer systems to work with existing plants. Because integration depends on specifics (plant configuration, capacities, temperature requirements), the best next step is a direct discussion to assess fit and define an approach.

   

• Q

  Among the application examples (industries, hospitals, universities, district energy), most concern large buildings. In the municipal sector we have many small/medium buildings (fire halls, police stations, libraries, arenas, aquatic centers). Are initial implementation costs higher, and is a financial ROI case needed beyond environmental benefits?

  At smaller scale, natural‑refrigerant heat pumps can have higher per‑unit costs, so a clear ROI case is important. One way to improve economics is to consider district or thermal‑energy‑sharing approaches linking multiple buildings and, where possible, moving heat from where it is rejected to where it is needed (for example, reclaiming heat from an ice rink). In arenas specifically, there is both an efficiency and cost‑savings opportunity to better integrate heating and cooling. Fully integrated, all‑in‑one solutions (e.g., combining the ice‑plant refrigeration with the heat‑pump functions in a single package) can reduce intermediate heat exchangers, loops, pumping, and controls complexity, improving efficiency and lowering total installed cost while simplifying operation.

   

   

• Q

  The higher efficiency you mentioned needs further justification.

  We agree. Some opportunities inherently deliver better efficiencies than others. The key is to identify the cases with the best thermodynamic fit—often involving lower required heating temperatures and the use of available heat‑recovery sources—as these tend to yield higher COPs and, in turn, stronger paybacks.

Note: These responses reflect guidance shared by our technical team during and immediately after the session and are intended as high‑level direction. Site‑specific engineering is required for design decisions.