Refrigerant Comparison Guide
Framework for comparing HVAC refrigerants. Five axes of comparison — thermodynamics, safety, environmental impact, regulation, and practical service factors — plus decision logic for the common scenarios where you need to choose between refrigerants.
1. The five comparison axes
Every refrigerant choice involves trade-offs across five distinct axes. A refrigerant that excels on one axis may be poor on another — and the binding axis depends on the decision context. For new equipment specification, regulatory phase-down status usually dominates. For service work on existing equipment, lubricant and safety-class compatibility dominate. For retrofit, pressure envelope match dominates.
The five axes:
- Thermodynamic — operating pressure envelope, volumetric capacity, temperature glide, critical point. These determine what equipment the refrigerant can work in and at what efficiency.
- Safety classification — ASHRAE Standard 34 toxicity (A/B) and flammability (1/2L/2/3). These determine equipment design requirements and field handling practices.
- Environmental impact — ozone-depletion potential (ODP), global warming potential (GWP), atmospheric lifetime. These drive regulatory phase-downs.
- Regulatory status— Montreal Protocol (ozone), EPA AIM Act / EU F-Gas Regulation (climate), SNAP acceptable-use designations. These determine what's legal for new equipment and service.
- Practical service factors — lubricant compatibility, equipment availability and cost, refrigerant cost trends, service complexity. These determine the day-to-day cost and difficulty of working with the refrigerant.
2. Thermodynamic axis: pressure, capacity, glide
The most fundamental refrigerant property is its pressure envelope — the relationship between temperature and saturation pressure across the operating range. Pressure envelope determines what equipment design the refrigerant fits and at what efficiency.
Saturation pressure at a standard reference temperature (70°F) is a useful one-number summary. Refrigerants sort naturally into pressure bands:
- Very high pressure (700+ PSIG @70°F): R-744 (CO₂) at ~838 PSIG. Requires equipment rated for very high pressures; transcritical operation in warm climates.
- High pressure (150-300 PSIG @70°F): R-410A (~202), R-32 (~206), R-454B (~190), R-404A (~149), R-507A (~153). The HFC and modern A2L workhorses.
- Medium-high pressure (100-150 PSIG @70°F): R-22 (~121), R-454C (~141 bubble), R-290 (~110). Includes the dominant historical residential refrigerant (R-22).
- Medium pressure (40-100 PSIG @70°F): R-134a (~71), R-513A (~77), R-450A (~57), R-1234yf (~74), R-1234ze (~49). The chiller and commercial cooling range.
- Low pressure (0-40 PSIG @70°F): R-123 (sub-atmospheric at typical chiller evap), R-1233zd(E) (~1.6), R-245fa (~16), R-1336mzz(Z) (sub-atmospheric). Low-pressure centrifugal chiller fluids.
- Sub-atmospheric (negative PSIG @70°F): R-123, R-514A, R-1336mzz(Z). Operating with the suction side below atmospheric is the normal regime for these fluids in their target equipment.
Temperature glideis the difference between bubble (saturated liquid) and dew (saturated vapor) temperatures at a given pressure. Pure refrigerants and azeotropic blends have zero glide; zeotropic blends have meaningful glide that requires equipment and service-procedure accommodation. High-glide blends (>10°F) include R-407C (~10°F), R-454C (~14°F), R-455A (~22°F), R-449A (~10°F). The superheat calculator uses the correct curve (dew for superheat, bubble for subcooling) automatically.
Critical temperature matters for refrigerants whose critical point is near typical ambient temperatures. R-744 (CO₂) has critical temperature 88°F — at outdoor ambient above 88°F, CO₂ cannot condense and must operate transcritically. R-13 (CFC, legacy) has critical temperature 84°F, limiting it to cascade low-stage roles. R-23 (HFC) at 79°F similarly. Most HVAC refrigerants have critical temperature well above ambient (R-410A ~163°F, R-134a ~214°F, R-22 ~205°F).
3. Safety axis: ASHRAE classification
ASHRAE Standard 34 assigns a two-character safety code to every refrigerant: a letter for chronic toxicity and a number/code for flammability. The grid below shows the eight possible classifications with examples.
| Class | Toxicity | Flammability | Examples |
|---|---|---|---|
| A1Non-flammable | Lower | Non-flammable | R-22, R-134a, R-410A, R-404A, R-744 |
| A2LMildly flammable | Lower | Mild (≤10 cm/s burning velocity) | R-32, R-454B, R-1234yf, R-1234ze |
| A2Flammable | Lower | Flammable | R-152a, R-365mfc |
| A3Highly flammable | Lower | Highly flammable | R-290, R-600a, R-1270 |
| B1Toxic, non-flammable | Higher | Non-flammable | R-123, R-245fa, R-514A |
| B2LToxic + mildly flammable | Higher | Mild | R-717 (ammonia) |
| B2Toxic, flammable | Higher | Flammable | (rare in HVAC) |
| B3Toxic, highly flammable | Higher | Highly flammable | (rare in HVAC) |
Why the safety class matters in practice:
- A1 (most legacy and current HVAC): No special equipment design required for flammability; standard service procedures.
- A2L (the modern transition class): Equipment must be A2L-rated — sealed motors, ignition-source isolation, leak detection where appropriate, charge limits per IEC 60335-2-40 and ASHRAE 15. Field service uses nitrogen-purged brazing (already standard for HFC service), A2L-compatible leak detectors. Retrofits from A1 to A2L are generally not permitted without OEM authorization.
- A2 (R-152a, R-365mfc): Substantially more restrictive than A2L due to faster flame propagation. Limited HVAC equipment uses A2.
- A3 (hydrocarbons):Highly flammable. Charge limits typically <150g for general applications under IEC 60335-2-40; commercial refrigeration limits per IEC 60335-2-89 allow somewhat larger charges in sealed equipment. Industrial refrigeration with proper engineering controls can use larger charges.
- B1 (R-123, R-245fa, R-514A): Higher chronic toxicity. Machine-room ventilation and leak detection per ASHRAE 15. Industrial hygiene practices during service (avoid prolonged inhalation).
- B2L (R-717 ammonia): Both higher toxicity AND mild flammability. Industrial-grade equipment with extensive engineering controls; typically not used in commercial or residential applications.
4. Environmental axis: ODP, GWP, atmospheric lifetime
Three closely-related environmental metrics drive most modern refrigerant decisions.
Ozone-depletion potential (ODP) measures how effectively a molecule destroys stratospheric ozone, relative to R-11 (defined as ODP 1.0). CFCs have high ODP (R-11 = 1.0, R-12 = 1.0, R-13 = 1.0). HCFCs have low but non-zero ODP (R-22 = 0.055, R-123 = 0.02, R-124 = 0.022). HFCs and HFOs have zero ODP. The Montreal Protocol (1987 and subsequent amendments) phased out CFCs (US: 1996) and HCFCs (R-22 in 2020, R-123 in 2020, R-124 in 2015). HFCs and HFOs have no ozone concern.
Global warming potential (GWP) measures the integrated radiative forcing of a molecule relative to CO₂ (defined as GWP 1.0) over a 100-year time horizon. GWP varies enormously across refrigerants: R-744 (CO₂) at 1, R-1234yf at 4, R-32 at 675, R-410A at 2088, R-404A at 3922, R-23 at 14800, R-c318 at 10300. The EPA AIM Act and EU F-Gas Regulation phase down HFCs based on GWP thresholds.
Atmospheric lifetime is the average residence time of a molecule before atmospheric removal (typically OH-radical attack for HFCs). Lifetime directly drives GWP — longer lifetime means more cumulative warming. Most HFCs have lifetimes of 5-50 years. PFCs (perfluorocarbons like R-218, R-c318) have lifetimes of 2000-50000 years because their fully-fluorinated structure resists atmospheric removal. CFCs and HCFCs have intermediate lifetimes (R-22 ~12 years, R-13 ~640 years).
The relationship: GWP ≈ (radiative efficiency per molecule) × (atmospheric lifetime), divided by CO₂'s reference value. Refrigerants with similar radiative properties differ in GWP primarily through lifetime differences. This is why structural isomers can have very different GWPs — R-236ea (lifetime 11 years, GWP 1370) versus R-236fa (lifetime 242 years, GWP 9810) are the same chemical formula with different fluorine arrangements producing dramatically different atmospheric behavior.
5. Regulatory axis: phase-out timelines
Four regulatory frameworks govern refrigerant decisions:
Montreal Protocol (1987, amended).International treaty mandating phase-out of ozone-depleting substances. US implementation through the Clean Air Act Section 605/606. CFC production banned 1996. HCFC production phase-out: R-141b banned 2003; R-22 banned 2020; R-123 banned 2020. The Montreal Protocol's Kigali Amendment (2016, US ratified 2022) extends to HFC phase-down.
EPA AIM Act (2020, implementing Kigali Amendment). US HFC phase-down under EPA SNAP implementation. Targets include R-410A, R-404A, R-134a, R-407C, R-32, R-125, R-143a, R-227ea, others. Key dates: 2022-2024 production allocation reductions; January 1, 2025 new-equipment restrictions for residential AC (R-410A new equipment significantly restricted, transitioning to A2L); January 1, 2025 similar restrictions for commercial refrigeration; January 1, 2026 additional restrictions for chillers and heat pumps. The phase-down continues through 2036.
EU F-Gas Regulation 517/2014 (revised 2024). European HFC phase-down with quota-based production controls and equipment-segment GWP thresholds. 150-GWP threshold for some commercial refrigeration and small split AC; 750-GWP threshold for chillers; 2500-GWP threshold for centralized commercial refrigeration. The 2024 revision tightens schedules further through 2030.
EPA SNAP (Significant New Alternatives Policy). US program listing acceptable substitutes for ozone-depleting substances by end-use category. SNAP listings determine which refrigerants are legally usable in which equipment segments. Most modern HFOs and A2L blends have SNAP acceptable-use designations for their target applications.
What this means for decisions:
- New residential AC equipment (US, 2025+): R-410A is restricted. R-32 and R-454B are the A2L replacements. R-22 is banned for new equipment.
- New commercial refrigeration (US, 2025+): R-404A and R-507A are restricted for many end-use categories. R-448A, R-449A, R-454C, R-455A, R-744 are the alternatives.
- New chillers (US, 2026+): R-134a and R-410A are restricted for many applications. R-450A, R-513A, R-515A, R-515B, R-1234ze(E), R-1233zd(E) are the alternatives.
- Existing equipment (any age): Continues to be serviceable with the original refrigerant indefinitely under current rules. Service supply is reclaimed for phased-out refrigerants (R-22, R-123, etc.) — finite and shrinking.
6. Practical axis: lubricant, cost, service
Beyond thermodynamics and environment, day-to-day practical factors determine the actual cost and difficulty of working with a refrigerant.
Lubricant compatibility is the most common gotcha. Mineral oil (MO) and alkylbenzene (AB) are compatible with CFCs and HCFCs (R-22 era). Polyolester (POE) is required for HFCs and HFOs (R-410A, R-134a, R-32, R-1234yf, etc.). Polyvinyl ether (PVE) is used with some HFCs in specific equipment. Polyalkylene glycol (PAG) is used with some HFO chillers and in mobile AC (R-134a, R-1234yf). Mixing incompatible lubricants causes oil breakdown and refrigerant decomposition — a hard-to-diagnose failure mode. The retrofit compatibility calculator checks lubricant compatibility for any refrigerant pair.
Equipment availability and cost. A1 refrigerant equipment (R-22, R-134a, R-410A, R-404A equipment) has been mass-produced for decades — wide availability, competitive pricing. A2L equipment (R-32, R-454B, R-1234yf) is becoming standard but currently carries a modest price premium and limited installer familiarity. A3 hydrocarbon equipment (R-290) is widely available in EU markets but more limited in the US. Specialty equipment (R-744 CO₂ chillers, R-717 ammonia industrial systems) has limited supplier base and significant capital cost premiums.
Refrigerant cost trends. Reclaimed R-22 (phased out 2020) is increasingly expensive as supply tightens. R-410A pricing has risen sharply as AIM Act production allocations decrease through 2025. R-32 and R-454B carry modest premiums as a-2L blends. Hydrocarbons (R-290) are inexpensive but charge-limited. R-744 (CO₂) is essentially free but the equipment is expensive. R-717 (ammonia) is inexpensive but only deployable in industrial settings.
Service complexity increases with safety class: A1 is simplest, A2L adds modest procedures (nitrogen-purged brazing, A2L leak detector, A2L recovery cylinders), A3 requires intrinsically safe equipment in the refrigerant space and explicit hydrocarbon-rated training, B1 requires industrial hygiene practices, B2L (ammonia) requires extensive industrial-scale safety infrastructure.
7. Decision frameworks
Scenario A: New residential AC equipment, 2026+
The choice in 2026 is between R-32 (pure HFC, A2L, GWP 675) and R-454B (HFC/HFO blend, A2L, GWP 466). Both replace R-410A in new equipment. The decision typically follows the equipment OEM's standardization: Daikin favors R-32 (pure-component supply chain control); Carrier, Trane, Lennox favor R-454B (slightly lower GWP, blend manufactured by Honeywell/Chemours). Performance is comparable. R-32 has marginally higher discharge temperature (different compressor sizing); R-454B has small (~2°F) glide. Both are A2L — equipment design accommodations are similar.
Tie-breakers: equipment availability in your market, installer familiarity, OEM service support, refrigerant supply security.
Scenario B: Existing R-22 residential AC, 2026
Repair vs replace hinges on equipment age, leak history, and economics. Under 10 years with no leaks: continue on reclaimed R-22 (legal, available at premium prices). 10-15 years with isolated leak: repair and consider retrofit blend (R-422D, R-407C, R-438A). Over 15 years or multiple leaks: replace with new R-32 or R-454B equipment.
R-22 retrofit blends face their own AIM Act restrictions — they're a bridge, not a destination. Replacement with new low-GWP equipment also delivers 20-30% efficiency improvement that aids payback.
Scenario C: Commercial refrigeration, R-404A path
R-404A (GWP 3922) faces aggressive AIM Act phase-down. For new equipment: R-448A or R-449A (medium-GWP, A1, drop-in for R-404A retrofit), R-454C or R-455A (low-GWP, A2L), or R-744 (CO₂ transcritical) depending on scale and capital availability. For existing R-404A equipment: R-448A and R-449A are mineral-oil-compatible retrofit options that buy time; R-454C and R-455A retrofits require A2L equipment evaluation.
Supermarket-scale operations have increasingly moved to R-744 CO₂ booster systems for long-term GWP compliance — significant capital investment but eliminates HFC phase-down risk.
Scenario D: Centrifugal chiller, R-123 / R-134a transition
R-123 was the dominant low-pressure centrifugal chiller refrigerant for decades — production banned 2020. Replacement options: R-1233zd(E) (HFO, A1, GWP 1, near-drop-in pressure envelope), R-1224yd(Z) (HCFO, A1, GWP 1), R-514A (HFO blend, B1 toxicity classification, GWP 2). R-1233zd(E) leads in market share.
R-134a chillers face AIM Act restrictions for new equipment. Replacement options: R-513A (A1, GWP 631), R-450A (A1, GWP 605), R-515A (A1, GWP 392), R-515B (A1, GWP 287), or pure R-1234ze(E) (A2L, GWP 7). The A1 blends are retrofit-compatible with existing R-134a equipment; R-1234ze(E) requires new A2L-rated equipment.
Scenario E: Heat pump for industrial process heat (80-150°C)
High-temperature industrial heat pumps require working fluids with high-temperature stability and appropriate pressure envelope. R-245fa was historical workhorse for organic Rankine cycle and heat-pump applications; being replaced by R-1233zd(E) (A1, GWP 1) for moderate-temperature applications and R-1336mzz(Z) (A1, GWP 2) for high-temperature applications (up to 150°C condensing). R-1234ze(Z) also serves the high-temperature heat-pump range.
EU Heat Pump Action Plan and US IRA industrial heat-pump credits are driving rapid growth in this segment — equipment OEMs are still consolidating around specific refrigerant choices.
8. Comparison tables by application
Residential and light commercial AC
| Refrigerant | Class | GWP | ODP | PSIG @70°F | Glide °F | Status |
|---|---|---|---|---|---|---|
| R-22 | A1Non-flammable | 1810 | 0.055 | 121 | 0.0 | Phased out |
| R-410A | A1Non-flammable | 2088 | 0 | 202 / 201 | 0.2 | Affected |
| R-32 | A2LMildly flammable | 675 | 0 | 206 | 0.0 | Affected |
| R-454B | A2LMildly flammable | 466 | 0 | 191 / 183 | 2.3 | — |
| R-454C | A2LMildly flammable | 148 | 0 | 141 / 112 | 13.9 | — |
R-22 was the dominant residential AC refrigerant from 1960s-2010; R-410A took over from 2010-2024; R-32 and R-454B are the post-AIM-Act standards. R-454C is for low-temp applications.
Commercial refrigeration (R-404A path forward)
| Refrigerant | Class | GWP | ODP | PSIG @70°F | Glide °F | Status |
|---|---|---|---|---|---|---|
| R-404A | A1Non-flammable | 3922 | 0 | 149 / 147 | 0.9 | Affected |
| R-507A | A1Non-flammable | 3985 | 0 | 153 | 0.0 | Affected |
| R-448A | A1Non-flammable | 1387 | 0 | — | 11.5 | Affected |
| R-449A | A1Non-flammable | 1397 | 0 | 151 / 129 | 9.5 | Affected |
| R-454C | A2LMildly flammable | 148 | 0 | 141 / 112 | 13.9 | — |
| R-455A | A2LMildly flammable | 148 | 0 | 170 / 121 | 21.6 | — |
R-404A and R-507A are the high-GWP legacy refrigerants under AIM Act phase-down. R-448A and R-449A are medium-GWP A1 retrofits; R-454C and R-455A are low-GWP A2L alternatives for new equipment.
Centrifugal chillers (R-134a and R-123 transition)
| Refrigerant | Class | GWP | ODP | PSIG @70°F | Glide °F | Status |
|---|---|---|---|---|---|---|
| R-123 | B1Toxic, non-flammable | 77 | 0.02 | -3 | 0.0 | — |
| R-134a | A1Non-flammable | 1430 | 0 | 71 | 0.0 | Affected |
| R-513A | A1Non-flammable | 631 | 0 | 77 | 0.0 | Affected |
| R-450A | A1Non-flammable | 605 | 0 | — | 0.9 | Affected |
| R-515B | A1Non-flammable | 293 | 0 | — | 0.0 | — |
| R-1234ze | A2LMildly flammable | — | 0 | 49 | 0.0 | — |
| R-1233zd(E) | A1Non-flammable | 1 | 0.00034 | 2 | 0.0 | — |
R-123 (banned 2020) and R-134a are the historical chiller refrigerants. R-513A and R-450A are A1 retrofits for R-134a. R-1234ze(E) and R-1233zd(E) are very-low-GWP next-generation choices (A2L and A1 respectively).
Natural refrigerants
| Refrigerant | Class | GWP | ODP | PSIG @70°F | Glide °F | Status |
|---|---|---|---|---|---|---|
| R-744 | A1Non-flammable | 1 | 0 | 838 | 0.0 | — |
| R-717 | B2LToxic + mildly flammable | 0 | 0 | 114 | 0.0 | — |
| R-290 | A3Highly flammable | 3 | 0 | 110 | 0.0 | — |
| R-600a | A3Highly flammable | 3 | 0 | 31 | 0.0 | — |
| R-1270 | A3Highly flammable | 2 | 0 | 137 | 0.0 | — |
| R-1234yf | A2LMildly flammable | — | 0 | 74 | 0.0 | — |
Natural refrigerants and HFOs with very low GWP. R-1234yf (a low-GWP HFO, not strictly a 'natural') included for comparison — it's the dominant mobile AC refrigerant. Application-specific suitability: R-744 for commercial refrigeration; R-717 for industrial; R-290/R-600a/R-1270 for small commercial and EU residential heat pumps.
9. FAQ
›What's the single most important axis when comparing refrigerants?
It depends on the decision. For new equipment specification, regulatory phase-down status often dominates — picking a refrigerant facing imminent restriction creates stranded-asset risk. For service decisions on existing equipment, lubricant compatibility and safety class compatibility with the equipment design dominate. For retrofit decisions, pressure envelope match and capacity match are critical. The 5-axis framework forces you to consider all of them, but in practice one axis is usually the binding constraint for a given decision.
›Why is the industry transitioning from R-410A to R-32 and R-454B?
GWP. R-410A is GWP 2088 (IPCC AR5) and is restricted under the EPA AIM Act for new equipment beginning January 1, 2025 (with regulatory phase-down through 2036). R-32 (GWP 675) and R-454B (GWP 466) are the dominant A2L replacements. R-32 is the pure-component choice (Daikin's preference); R-454B is a R-32/R-1234yf blend (Carrier, Trane, Lennox preference). Both require A2L-rated equipment with sealed motors, charge limits, and leak-detection accommodations. Equipment built before the transition uses R-410A and continues to be serviceable with reclaimed R-410A indefinitely.
›Is a lower-GWP refrigerant always better?
No — it's a multi-axis trade-off. The lowest-GWP refrigerants (hydrocarbons R-290, R-600a, R-1270 at GWP 2-3) are A3 highly flammable and charge-limited under most codes. R-744 (CO₂, GWP 1) is non-flammable but requires very-high-pressure equipment and transcritical operation in warm climates. R-1234yf (GWP 4) and R-1234ze (GWP 7) are A2L. The 'low-GWP doesn't necessarily mean drop-in' point is the foundation of the modern transition — switching refrigerants typically requires new equipment, not just new refrigerant.
›Should I retrofit an R-22 system or replace it?
Depends on age, condition, and economics. For systems under 10 years with no leaks and intact compressor, retrofit to an HFC like R-422D or R-407C is reasonable — but only buys time, because those refrigerants face their own AIM Act restrictions. For systems over 15 years, multiple leaks, or with compressor concerns, full replacement with new R-32 or R-454B equipment is typically more cost-effective. New equipment is also 20-30% more efficient than R-22-era equipment, which improves the payback.
›Why do natural refrigerants get so much attention if they're not widely deployed?
They're the ultimate destination if the regulatory phase-down continues to its logical conclusion. R-744 (CO₂), R-290 (propane), R-600a (isobutane), and R-717 (ammonia) all have GWP under 10 and are not subject to any phase-down. Limitations on widespread deployment: R-744 requires expensive transcritical equipment in warm climates; R-290/R-600a/R-1270 are A3 with charge limits; R-717 is B2L (mildly toxic and mildly flammable) and used primarily in industrial settings. The transition is happening but gradually — heat pumps with R-290, supermarket refrigeration with R-744 CO₂ booster, industrial chillers with R-717.
›What's the difference between azeotropic and zeotropic blends?
Azeotropic blends have effectively zero temperature glide — bubble and dew points coincide at typical operating pressures. Service measurement of superheat and subcooling can be done without distinguishing bubble vs dew curves (treat like a pure refrigerant). R-410A and R-507A are near-azeotropes; R-500 and R-502 are true azeotropes (legacy). Zeotropic blends have meaningful glide (R-407C ~10°F, R-454C ~14°F, R-455A ~21°F). Service requires using the dew curve for superheat and bubble curve for subcooling. The PT calculator and related tools handle this automatically.
›What does ASHRAE 34 safety classification mean?
A two-character classification: the letter (A/B) indicates chronic toxicity (A = lower, B = higher); the number (1/2L/2/3) indicates flammability (1 = non-flammable, 2L = mildly flammable with low burning velocity ≤10 cm/s, 2 = flammable, 3 = highly flammable). Common classifications: A1 (R-22, R-134a, R-410A, R-404A — non-flammable, lower toxicity); A2L (R-32, R-454B, R-1234yf — mildly flammable, lower toxicity, the modern transition class); A3 (R-290, R-600a, R-1270 — highly flammable, lower toxicity); B1 (R-123, R-245fa — non-flammable, higher toxicity); B2L (R-717 ammonia — mildly flammable, higher toxicity).
›How does temperature glide affect equipment selection?
High-glide blends (>10°F) need TXV systems that can adjust to the operating-condition saturation profile; fixed-orifice systems aren't well-matched to high-glide blends. The bubble-to-dew temperature spread at the evaporator inlet creates a temperature 'profile' across the evaporator that affects heat transfer coefficient and frost behavior. Modern A2L blends like R-454C (14°F glide) and R-455A (21°F glide) are designed for TXV or EXV equipment with appropriate adjustment. R-410A (azeotrope, near-zero glide) works well with both TXV and fixed-orifice systems.
PT Comparison Tool
Overlay 2-4 refrigerants on a single PT chart for visual comparison.
Retrofit Compatibility
Pair-comparison decision: lubricant, safety, pressure, glide, application overlap.
Safety Class Index
All 61 refrigerants sorted by ASHRAE class with phase-down status.