Best Refrigerant for Heat Pumps: Options, Efficiency, and Regulations

Choosing the best refrigerant for a heat pump balances efficiency, environmental impact, safety, cost, and regulatory compliance. This article compares leading refrigerant choices, explains trade-offs, and outlines what homeowners and technicians should consider when specifying or replacing refrigerants.

Refrigerant	GWP	Flammability	Suitability	Notes
R410A	~2088	Non-flammable	Existing systems (phasing out)	High GWP; being phased out by regulations
R32	~675	Mildly Flammable (A2L)	New residential systems	Good efficiency; growing global adoption
R454B	~466	Low Flammability (A2L)	New split systems and small heat pumps	Lower GWP; retrofit compatibility varies
R290 (Propane)	<1	Highly Flammable (A3)	Small charged systems	Excellent thermodynamics; safety and code limits
R744 (CO2)	1	Non-flammable	Commercial/Cold-Climate Heat Pumps	High pressure systems; efficient for transcritical cycles
R1234yf / R1234ze	<1 to 7	Low Flammability (A2L)	Specialized applications	Low GWP; cost and performance vary

How Refrigerants Impact Heat Pump Performance

Refrigerant choice directly affects compressor work, heat transfer rates, operating pressures, and seasonal energy efficiency. A refrigerant with favorable thermodynamic properties can lower electricity use and improve heating capacity in cold climates.

Key Performance Metrics: Cooling/heating capacity, coefficient of performance (COP), volumetric refrigeration capacity, and pressure ratios determine how well a refrigerant suits a given heat pump design.

Environmental Considerations: GWP And Ozone Depletion

Global Warming Potential (GWP) and Ozone Depletion Potential (ODP) are central to refrigerant selection in the U.S. High-GWP refrigerants are targeted for phase-down under federal and state regulations.

Regulatory Drivers: The U.S. EPA SNAP rules and state initiatives push manufacturers toward low-GWP alternatives, accelerating the industry transition from legacy refrigerants like R410A to A2L refrigerants and other low-GWP options.

Common Refrigerant Options And Trade-Offs

R410A

R410A has been the dominant refrigerant for modern residential heat pumps due to its non-flammable nature and reliable performance. However, its high GWP makes it subject to phase-down schedules.

Pros: Non-flammable, well-understood service practices, widespread availability. Cons: High GWP, increasing regulatory restrictions, limited future use.

R32

R32 (difluoromethane) is increasingly used in residential heat pumps. It offers improved efficiency and lower GWP versus R410A but is classified as mildly flammable (A2L).

Pros: Better energy efficiency, lower GWP than R410A, growing manufacturer support. Cons: Requires updated safety protocols and installer training due to A2L classification.

R454B And Other HFO/HFC Blends

R454B and similar HFO/HFC blends were developed to reduce GWP while maintaining favorable system pressures and performance similar to R410A.

Pros: Lower GWP (hundreds vs. thousands), designed for retro-fit potential in some systems. Cons: Mild flammability, variable compatibility with existing oils and materials, evolving availability and pricing.

R290 (Propane)

R290 has a near-zero GWP and excellent thermodynamic characteristics. It is attractive for small-charge heat pumps and ductless mini-splits.

Pros: Extremely low GWP, high efficiency, low cost. Cons: Classified as highly flammable (A3), strict charge limits, and code restrictions limit broad residential use.

R744 (CO2)

CO2 is an ultra-low GWP refrigerant suitable for specialized transcritical systems and cold-climate heat pumps where high pressure equipment is acceptable.

Pros: GWP of 1, non-flammable. Cons: Requires high-pressure components, specialized compressors, and different design considerations that increase initial cost.

Low-GWP HFOs (R1234yf / R1234ze)

HFO refrigerants have very low GWPs and appear in some new heat pump designs. Their use is expanding but they can be more expensive and may require design changes.

Pros: Very low GWP; suitable for many modern designs. Cons: Cost, aging data on long-term reliability, and some mild flammability classifications.

Safety, Building Codes, And Installer Requirements

Flammability and toxicity categories (A1, A2, A3, B1) dictate safe charge sizes, ventilation, and equipment placement. New A2L refrigerants require updated safety standards, technician training, and appropriate labeling.

Practical Safety Notes: Systems using A3 refrigerants like R290 require explosion-proof practices and limited charge sizes. Local building codes and fire codes may restrict where and how flammable refrigerants are used.

Retrofit Vs. New Equipment: Compatibility Issues

Retrofits of existing R410A systems to low-GWP refrigerants are sometimes proposed, but compatibility must be evaluated for oil type, component pressures, lubricant miscibility, and safety certification.

Important Considerations: Many low-GWP A2L refrigerants require different lubricants and may have different pressures, meaning a true retrofit may not be straightforward or approved by the original equipment manufacturer (OEM).

Cost And Availability

Pricing varies with supply chain dynamics, global demand, and regulatory changes. Newer low-GWP refrigerants can be more expensive initially, but total lifecycle costs often favor more efficient, low-GWP systems.

Lifecycle Cost Factors: Energy savings, refrigerant price, maintenance costs, potential need for specialized service tools, and regulatory compliance fines or restrictions.

Choosing The Right Refrigerant For Different Scenarios

Residential Ducted Heat Pumps

For new residential ducted systems, A2L refrigerants like R32 or R454B are commonly selected for a balance of efficiency and lower GWP, provided installers follow A2L safety rules.

Ductless Mini-Splits

Ductless systems often use R32 or R290 depending on manufacturer design and charge limits. R290 offers best-in-class environmental performance but faces stricter charge limits.

Cold-Climate Heat Pumps

In cold climates, refrigerants with excellent low-temperature performance such as R32 and CO2 (in specialized designs) can deliver superior heating capacity and efficiency.

Commercial Applications

Commercial systems may use R744, low-GWP HFO blends, or engineered refrigerant blends tailored to large-capacity needs, safety codes, and service logistics.

Installation, Servicing, And Maintenance Best Practices

Technicians must be certified under EPA Section 608 and trained on new refrigerants, especially A2L and A3 classifications. Proper leak detection, evacuation, and charging procedures protect performance and safety.

Maintenance Tips: Check for oil compatibility, maintain correct charge, verify pressure and superheat/subcooling, and ensure system labeling reflects the refrigerant type.

Future Trends And What To Expect

The industry trend favors low-GWP refrigerants and electrification of heating. A2L refrigerants and hydrocarbons will likely increase in use for residential units while CO2 and optimized HFOs grow in commercial niches.

Policy Impact: Continued regulatory pressure on high-GWP refrigerants will accelerate retirements of R410A and similar blends in favor of lower-GWP options.

Practical Recommendation Summary

For most U.S. residential heat pumps, R32 or R454B represent practical, efficient, and lower-GWP choices for new equipment when contractor expertise and local codes allow. R290 is ideal where charge limits and codes permit for ultra-low-GWP installations. R744 is best for specialized commercial or cold-climate systems. Avoid retrofitting high-GWP R410A systems without OEM approval and detailed compatibility checks.

How To Decide For A Specific Project

1. Verify local and state codes regarding A2L and A3 refrigerants.
2. Consult OEM specifications for approved refrigerants and retrofit guidance.
3. Evaluate energy performance (HSPF, SEER, COP) for the refrigerant-equipped model.
4. Assess installer certification and experience with the chosen refrigerant class.
5. Consider lifecycle costs including electricity consumption and projected refrigerant availability.

Resources And Further Reading

Refer to EPA SNAP listings, AHRI technical guidance, manufacturer datasheets, and local building codes for the latest approved refrigerant uses and restrictions. Professional HVAC organizations publish best practices for A2L handling and system design.

Key Sources: U.S. EPA, Air-Conditioning, Heating, and Refrigeration Institute (AHRI), National Fire Protection Association (NFPA) codes, and OEM installation manuals provide up-to-date technical and regulatory details.

If additional detail is needed regarding a specific refrigerant, heat-pump model, or local code interpretation, consulting a certified HVAC professional or the equipment manufacturer is recommended.