TECHNOLOGY IMPROVEMENTS likely to reach the market within two years will improve conventional air-to-air heat pump efficiency by perhaps 10 percent or more while reducing the climate risks of refrigerant leaks.  The improvements will involve a shift in the refrigerant chemicals used within the pumps.

From an environmental perspective, it may make sense for some homeowners, especially those who heat with gas and who do not have an immediate need to replace their heating system, to wait for the next generation of heat pumps. During that pause, consumers could focus on improving the insulation and general energy efficiency of their homes.

Heat pumps have been around for a century in various applications — air conditioners, chillers, refrigerators, ice machines. The set of chemicals available to use as refrigerants in heat pumps has been well studied. The last few decades of changes in refrigerants have reflected evolving public policy more than chemical innovation.

Since the world banned ozone-depleting refrigerants, the refrigerant most used in heat pumps in the United States has been a chemical mix known as R-410A.  R-410A is a very potent greenhouse gas.  Each pound of R-410A released into the atmosphere does roughly as much warming damage as a ton of carbon dioxide.

Refrigerant leaks are an important source of environmental damage and the EPA is engaged in rule-making which will effectively ban sales of heat pumps using R-410A after January 1, 2026 (banning new manufacture even sooner, by January 1, 2025).

EPA tailored its proposed limits to reflect the availability of substitutes. There are ready alternatives to R-410A, notably R-32, which is only about one-third as damaging to the environment as R-410A and would remain legal under the new rule. R-32 is already heavily used elsewhere in the world and many manufacturers see it as the successor to R-410A.

To allow R-32 and other alternatives to R-410A, we will need to accept refrigerants that are mildly flammable and this will require modifications to building codes. The code changes are likely to involve requirements for leak detection, circulating fans, labeling, and handling instructions. Additionally, the new rules may limit the ratio of heat pump refrigerant charge (weight of refrigerant contained) to the size of the space it could leak into — one wants to avoid the possibility that a full leak could create an air mix with a high enough concentration of mildly flammable refrigerant to ignite.

The previous policy choice of less-efficient, non-flammable refrigerants was driven by safety considerations, but the consensus seems to be that we can address safety considerations with appropriate controls and rules.

Overall, these regulatory changes and related industry adjustments to heat pump products appear to be good for consumers. As manufacturers move to refrigerants like R-32, we can expect an improvement in heat pump performance, perhaps 10 percent greater efficiency, meaning less electricity use, lower operating costs, and greater net environmental benefits. Ultimately, the performance improvements achieved will depend on careful engineering by the major competing manufacturers.

The likely 10 percent efficiency improvement expected from the heat pumps to be available soon will result in a considerably larger percentage increase in net greenhouse gas reductions in heat pump conversions from natural gas.  In conversions from natural gas, the difference between the carbon saved from reducing fossil fuel and the increased carbon costs of electricity generation is relatively small. For those conversions, the lifetime net greenhouse gas savings from a more efficient pump would likely exceed the greenhouse gas costs of a couple of years of delay. Those consumers who heat with gas and do not have an immediate need to replace a heating system may wish to wait for the better heat pumps.

For people who already have R-410A refrigerant pumps, the change does not create an imminent problem. However, over the next 10 or 15 years, R-410A may become scarcer and more expensive to acquire for the purpose of replacing leaked refrigerant.

Looking five or ten years out, there is room for further improvement. New propane-based pumps may offer even higher efficiency. Of course, propane is highly flammable. However, we may eventually see safe, factory-sealed propane heat pumps that do not circulate refrigerant to indoor units. They will do all their heat pumping outside, heating a reserve of water or glycol which is then circulated indoors, conceivably through radiators. This could solve a huge conversion obstacle for older New England homes that have hot water radiators.

William Brownsberger is a state senator from Belmont.

A longer version of this post with reference links appears at willbrownsberger.com.