Improving room AC energy efficiency and transitioning to low-GWP refrigerants simultaneously presents significant opportunities to deploy energy-efficient technology. 

HFCs are currently the fastest growing category of greenhouse gases (GHGs) and are used as refrigerants in AC and refrigeration systems, as foam-blowing agents for insulation, and among other uses as alternatives to CFCs and HCFCs. This growth is driven by AC and refrigeration demand from emerging economies with hot climates and rising incomes which are also undergoing rapid urbanization and electrification.

HCFCs are scheduled to be completely phased out by 2030 in non-A5 and A5 parties, in accordance with the Kigali Amendment. Phasing out CFCs and HCFCs has increased the demand for other refrigerants, particularly HFCs. HFCs do not contain any chlorine atoms and have near-zero ozone depletion potential (ODP), but many of them are very powerful GHGs. They are currently the fastest growing category of GHGs, growing at the rate of 10–15 percent per year.

HFCs and other fluorinated GHGs which include sulfur hexafluoride (SF6) and perfluorocarbons (PFCs) are already the fastest-growing climate pollutants globally. HFCs currently constitute less than 1 percent of the global radiative forcing from the climate. However, if the use of the current mix of HFCs were to continue following a business-as-usual scenario, increasing demand based on current market trends could significantly offset the climatic benefit achieved by the Montreal Protocol to date. In the air conditioning category, air-to-air ACs, representing mostly ductless mini-split units, dominate HFC use.

The new generation of refrigerants must offer high energy efficiency in addition to low GWP. Safety barriers, such as flammability and toxicity, also need to be addressed explicitly to make alternative refrigerants a viable solution. Alternatives with less environmental impact are often associated with a higher initial cost, so education on that issue will be necessary before wide-scale adoption can be realized. According to UNEP, the ideal refrigerant has characteristics such as being nontoxic, non-flammable, zero ODP, zero or low direct GWP, energy efficient, acceptable operating pressures, volumetric capacity appropriate to the application, low cost, and commercially available. In practical terms, the choice of refrigerant will likely involve trade-offs among one or more of the above criteria.

Low-GWP Refrigerants for ACs

Growth in the global AC market is primarily driven by stationary AC systems in emerging economies. HCFC-22 – that is, R-22 and HFC refrigerant blends are the most common refrigerants, with different energy efficiency ratings used in stationary room AC systems in most party countries to date.


The air conditioning sector accounts for 56 percent of current HFC consumption, and is projected to grow about 4.5 percent each year globally. From 2015 to 2050, HFC use in this sector in non-A5 parties and A5 parties is expected to grow 2 percent annually and 5.6 percent annually, respectively. Many low-GWP refrigerants that are currently available, or will become available in the near-term, provide GWP reductions of 50–75 percent or more compared to the most commonly used refrigerants. For example, R-32 with a GWP of 677 replaces R-410A, with a GWP of 1900.

Current Alternatives. Although the goal of the HFC phase-down is to replace current HFC refrigerants with low-GWP alternatives, R-32 is still considered a viable option for replacing current HFC refrigerants used in air conditioning applications with cooling capacity greater than about 5.2 kW (1.5 tons).

R-32 is a single-component refrigerant with a GWP of 677 and smaller system charge and is used as a replacement for R-410A, which has a GWP of 1900. R-32 is mildly flammable, with an A2L safety classification. The use of R-32 units in AC systems has accelerated in the past two years, with about 17 million units sold worldwide.

Hydrocarbons (HCs) are widely used in AC systems with smaller charge sizes. The most popular HC refrigerant used in AC systems is R-290 (propane). R-290 is completely halogen free, has no ODP, and a GWP value of 3 or less, but it is classified as an A3 refrigerant due to its high flammability. R-290 has many properties similar to R-22 and can have equal or higher efficiency compared to R-22 and R410A, depending on the ambient conditions. The flammability of HCs can be mitigated. However, the energy efficiency is lost if the equipment is designed to achieve a higher cooling capacity with a refrigerant charge smaller than optimal. R-290 is a technically feasible replacement for many R-410A systems, despite having slightly lower volumetric capacity and performance, so implementing it does not significantly reduce system efficiency so long as the refrigerant charge is large enough to achieve the rated capacity, mindful of the refrigerant volume contained in the pipe when the evaporator and condenser are far apart.

R-1270 is another HC, which is very similar to R-290 and listed as a low-GWP refrigerant alternative for ACs in UNEP (2015b), although there is not much interest from AC manufacturers to date.

R-290 and R-1270 are mainly considered for systems with smaller charge sizes, since the operating pressures and capacities are similar to R-22 and the efficiency is higher than R-22.

Emerging Refrigerants. Many manufacturers are also considering and evaluating new HFC/HFO blends, such as DR-55. It is a non-ozone depleting, HFC/HFO blend with a GWP of 698. It is proposed as a refrigerant replacement for R-410A in new equipment. It is mildly flammable with an A2L classification. The blend is 67 percent R-32, 7 percent R-125, and 26 percent R1234yf. DR-55 has the added advantage of being able to reuse components of R-410A.

The AHRI’s low-GWP Alternative Refrigerants Evaluation Program (AREP) tested the performance of refrigerants R-452B, R-32, DR-5A, ARM-71a, and L-41-2. The ORNL evaluation program also tested HFC/HFO blends R-447A, ARM71A, DR-3, ARM-20B, and R-444B as low-GWP refrigerants. However, other than the AHRI low-GWP AREP and the ORNL HAT program, there are no other publicly available energy-efficiency test results on those blends.

HFC-161, that is, R-161 is also currently under evaluation for systems with smaller charge size ACs, due to its flammability. The operating pressure and capacity of R-161 is similar to R-22, and the efficiency is at least as high as R-22, although there is concern about its stability.

Ammonia (NH3) and CO2 refrigerants are also listed as alternatives to high-GWP refrigerants. Ammonia has a GWP value of 0.21, while CO2’s GWP is 1. However, neither refrigerant is a likely candidate for room AC applications.

Emerging Efficiency Improvement Opportunities for ACs

Manufacturers have introduced several technologies that have collectively improved overall system efficiency, including: variable-speed drives; novel compressor, fan, motor, and heat exchanger designs; electronic expansion valves; and advanced controls. Various government and industry programs have also significantly increased the adoption of high-efficiency AC systems. The incremental cost of improving the efficiency of room ACs was based on the cost of improving the efficiency of its key components, and it was found that efficiency improvement of about 30 percent is cost effective in many countries.

Global HPMPs and Labeling Programs

In support of the implementation of national HPMPs developed, A5 parties have received assistance from UN environment, the United Nations Development Program (UNDP), the United Nations Industrial Development Organization (UNIDO), the World Bank, and the MLF in various areas, (UNDP, 2017), including:

  • institutional capacity building
  • assessment and demonstration of HCFC alternative technologies
  • technical assistance and technology transfer
  • support to maximize climate benefits in refrigeration and air conditioning
  • policy and regulatory interventions, and
  • increased access to funding

At the same time, more and more national governments are adopting domestic regulations to limit and reduce use of HFCs including:

  • limits on HFC use
  • bans on using HFCs in particular applications
  • fiscal incentives to reduce the price of HFC alternatives or increase price of HFCs
  • mandatory licensing of production
  • limits on imports or exports of HFCs, and
  • industrial requirements on the disposal, recovery, and management at end-of-life for HFCs, destruction of HFC-23

Both the continued development and implementation of second phases of HPMPs and national regulatory actions will be crucial to parties as they work toward meeting the Kigali amendment.

India, included under A5 of the Montreal Protocol, not only has a very large consumption of HCFCs (baseline: 1692 ODP tones), but also has a significant manufacturing base of HCFCs (baseline: 1608 ODP tones) and HVAC products. Having met its obligations to the Montreal Protocol by implementing phase-I of the HPMP, India has entered phase-II, which makes it very close to further strengthen its regulations, including the ones on energy efficiency, to implement the transition to low-GWP refrigerants.

The Government of India reported HCFC consumption of 992.54 ODP tones in 2015, which is 31.4 percent lower than the HPMP target of 1447.4 ODP tones for the same year in its agreement with the MLF Executive Committee, and 38.2 percent lower than the baseline of 1608.2 ODP tones.

According to UNEP, the growth in R-22 consumption is due to increased consumption of R-22 in RAC manufacturing and servicing. No HCFC-124 has been imported for the past three years. Currently, MEPS is mandatory for all domestic ACs except for inverter types, which will be covered by the mandatory MEPS from 2018. The star rating plan for both fixed and inverter ACs will merge in 2018 with the transition to the ISEER from the EER. In addition, EESL is currently working to develop a program for bulk procurement of superefficient ACs. Such a bulk procurement program would provide a significant opportunity for increasing AC efficiency and the use of low-GWP refrigerants in room ACs.

Transition to Low-GWP Refrigerants

The MLF Executive Committee stated that it is expected for approximately 95 A5 parties, stage-II HPMPs will address the remaining HCFC consumption mainly in the RAC sector, and the remaining HCFC-based manufacturing sectors not addressed in phase-I for parties with HCFC manufacturing. The availability of low-GWP alternatives has grown considerably in recent years, and new alternatives are being commercialized rapidly.

Given the anticipated focus on conversions in the RAC sector, phase-II of the HPMPs in parties with high-ambient temperatures and large or fast-growing air conditioning markets will be critical and will need technical assistance to integrate energy efficiency improvement into their transition plans. Many of these developing parties are also experiencing expanding populations and growing incomes, leading to further growth of the AC market and corresponding impacts on emissions, peak load, and electricity costs.

The principal barrier to wider deployment of low-GWP alternatives for ACs is safety. Other risks include capital cost and return on investment, and reliability. Most low-GWP alternative refrigerants are rated as Class A3 (flammable) or A2L (lower flammable) by ASHRAE Standard 15. To address the safety concern and lower the risk, three measures should be taken – fully evaluate and understand the risk, publish and adopt safety regulations, and develop training modules and standards for installing and servicing equipment with flammable refrigerants.

For ductless split ACs, development of R-32 has been led by Japanese manufacturers. For R-290 room ACs specifically, a recent risk assessment found that under normal usage conditions, a split AC with leakage amount of 382 g of R-290 has an 8.05 × 10–9 probability of causing a fire or explosion. A similar risk assessment on A2L refrigerant indicates that average risks associated with the use of the studied A2L refrigerants are significantly lower than the risks associated with other hazardous events, and also well below risks commonly accepted by the public in general. The Shanghai Quality Supervision, Inspection, and Quarantine Bureau will undertake safety and energy efficiency tests for new room AC models with flammable refrigerants produced by Chinese manufacturers before they enter the market.

Even though a number of safety codes and standards include the use of flammable refrigerants, most of today’s safety standards were developed prior to the current emphasis on low-GWP refrigerants. Many are under revision now to include the risk of A2L and A3 refrigerants in modern AC equipment. Changing refrigerants also requires system design changes before a product can be commercialized.

While actual costs under full-scale production conditions are unknown, future low-GWP refrigerants are expected to have a higher cost than the refrigerants they would replace. However, because refrigerant costs contribute roughly ~1 percent to total lifecycle AC system costs, initial cost increase owing to a low-GWP refrigerant transition is manageable. Refrigerant costs may not increase for systems that use refrigerants currently in mass production, such as R-32 and HCs, but new and more complex molecules, such as HFOs, are expected to be more expensive. Added cost may also come, at least initially, in systems that necessitate specialized component designs, increased heat exchanger size, higher operating pressures, or additional safety measures for flammable refrigerants. Nevertheless, performance test results of alternative refrigerants suggest that the cost barrier is addressable through both manufacturing advances and efficiency improvements that reduce lifecycle costs.

Moreover, policies ranging from demand-side management incentives, bulk procurement, and buyer’s clubs to minimum standards and labeling programs can help encourage development and deployment of energy efficient and climate friendly options that reduce lifecycle costs to consumers. In addition, necessary improvements in the level of training for production, installation, maintenance, and awareness of the general public in using products are needed to help address flammability concerns.

As more parties are strengthening their energy efficiency standards and mandatory or voluntary energy labeling programs, there are significant opportunities to simultaneously raise the mandatory efficiency requirements and add in voluntary or mandatory low-GWP criteria for ACs. The greatest opportunities to improve the efficiency of ACs lie in parties with MEPS or labeling programs that have relatively low MEPS requirements, or parties whose MEPS and labeling programs were revised prior to 2014 or are still under development. An additional opportunity to improve the average efficiency of the AC market is by combining product categories for fixed-speed and variable-speed AC products, based on the ISO standard 16358. The global market for super-efficient, low-GWP ACs also can be created through energy labeling programs that incorporate a low-GWP component as well as bulk procurement programs.

Some of the A5 parties are among the major global manufacturers of AC units and/or refrigerants, including China, India, and Thailand. Since both refrigerant transition and efficiency improvement require equipment redesign and manufacturing line retooling, ensuring all efforts are coordinated and have the potential to keep costs low for consumers and manufacturers is key for funding agencies such as the MLF.

In Conclusion

The refrigerant transition under the Kigali Amendment offers the opportunity to simultaneously improve the energy efficiency of the equipment, including that of room ACs. Furthermore, many parties have energy efficiency improvement policies such as standards, labels, and incentive programs which offer an opportunity for adoption of a low-GWP criterion in tandem. Market potential in emerging economies is very high for a number of reasons, including hot climate, growing incomes, increased electrification, and growing urbanization – and also because relatively small proportions of the large and growing population currently own ACs.

In the near future, reductions in high-GWP HFCs likely will be achieved by some combination of energy efficient HFCs, HFOs, HCs, and other emerging low-GWP refrigerant blends. Outdated and relatively lax MEPS for ACs globally, as well as continuing rapid growth in cooling demand, present an opportune time to improve the energy efficiency criteria of new ACs through more stringent MEPS and programs, developed through regional cooperation and with potential harmonization, which promote the adoption of super-efficient ACs. Outdated and low MEPS for ACs globally, as well as continuing rapid growth in cooling demand, present an opportunity to improve the energy efficiency criteria for new ACs through updated energy performance standards and labeling programs.

A simultaneous focus on and transition to the use of low-GWP alternative refrigerants in new ACs can maximize the reduction of energy, peak electricity demand, and GHG emissions associated with air conditioning use. Developing regulatory norms in advance will give manufacturers sufficient lead time to research, develop, and deploy new technologies, which will benefit parties where air conditioning manufacturing conversion has not been completed yet. Upgrading technology for both efficiency improvement and low-GWP refrigerant transition simultaneously will reduce costs and ease the burden on manufacturers’ design cycles, which typically occur at two- to three-year intervals. Finally, the risk of obsolete technology being deployed in markets that either have not updated their standards or have later compliance dates can be mitigated by updating standards and reviewing them periodically to ensure their effectiveness.

Opportunities for Simultaneous Efficiency Improvement and Refrigerant Transition in Air Conditioning – A report by Energy Analysis and Environmental Impacts Division, Lawrence Berkeley National Laboratory.