Natural Refrigerants: R290, R744, R717, R600a & Low-GWP Cooling
Natural refrigerants are naturally occurring substances used as refrigerants rather than purpose-made fluorinated refrigerants. Major HVAC/R examples include propane (R290), isobutane (R600a), carbon dioxide (R744), ammonia (R717) and propylene (R1270).
What are natural refrigerants?
Industry references commonly distinguish naturally occurring refrigerants from synthetic refrigerants. The most important modern HVAC/R groups are hydrocarbons, carbon dioxide and ammonia, with water and air used in more specialist applications.
Natural refrigerants are a family of very different working fluids
They share a naturally occurring origin, but they do not share one pressure range, one safety class or one ideal application. Selection still begins with the system architecture.
Hydrocarbons
Propane, isobutane and propylene offer very low GWP but commonly carry A3 flammability classifications.
Carbon Dioxide
R744 has GWP 1 and A1 classification but operates in a distinct high-pressure architecture.
Ammonia
R717 is a major industrial refrigerant with B2L classification and specific site, materials and safety requirements.
Water
R718 appears in specialist cooling and absorption-related contexts; it should not be treated like a mainstream vapor-compression replacement.
Air
R729 is used in specialist air-cycle and cryogenic/process contexts rather than as a general-purpose HVAC refrigerant.
Natural refrigerants compared by system role
The major natural refrigerants offer very low direct climate impact, but each brings a different combination of pressure, flammability, toxicity and equipment architecture.
| Refrigerant | Common Name | GWP / Climate Note | Safety | Typical System Role | Key Design Consideration |
|---|---|---|---|---|---|
| R290 | Propane | 3.3 | A3 | Heat pumps, commercial refrigeration, selected self-contained equipment | Flammability / charge / architecture |
| R600a | Isobutane | 1 | A3 | Domestic refrigeration and small-charge systems | Purpose-designed small-charge equipment |
| R744 | Carbon dioxide | 1 | A1 | Supermarkets, heat pumps, water heating, transport, specialist refrigeration | High-pressure architecture |
| R717 | Ammonia | 1 | B2L | Industrial refrigeration, cold storage, process cooling, industrial heat pumps | Site design, materials and toxicity management |
| R1270 | Propylene | 1.8 | A3 | Commercial / industrial specialist route | Hydrocarbon flammability constraints |
| R718 | Water | Very low direct climate impact | Specialist context | Specialist chillers / absorption-related systems | Vacuum / system architecture and application limits |
| R729 | Air | No forced site-wide GWP value | Specialist context | Air-cycle / cryogenic and process applications | Specialized cycle and equipment design |
R290, R600a, R744, R717 and R1270
These refrigerants are often grouped together under the word “natural,” but their system architectures are fundamentally different.
R290 — Propane
Hydrocarbon · GWP 3.3R290 is a major very-low-GWP route in purpose-designed heat pumps and refrigeration equipment. Its A3 classification makes refrigerant quantity, product architecture and applicable standards central to the design.
R290 profile →R600a — Isobutane
Hydrocarbon · GWP 1R600a is strongly associated with household refrigerators and freezers. It performs its role in purpose-designed, typically small-charge systems and should not be treated as a universal replacement for another refrigerant.
R600a profile →R744 — Carbon Dioxide
Natural refrigerant · GWP 1R744 appears in supermarket refrigeration, heat pumps, water heating, transport and specialist systems. Its A1 classification does not mean low pressure or simple equipment: the pressure architecture and critical-region behavior are central.
R744 profile →R717 — Ammonia
Natural refrigerant · GWP 1R717 is one of the most important industrial refrigerants, with strong roles in cold storage, process cooling and industrial heat pumps. Its B2L classification and materials compatibility shape the site and system design.
R717 profile →R1270 — Propylene
Hydrocarbon · GWP 1.8R1270 is a specialist hydrocarbon route used in selected commercial and industrial refrigeration applications. Like other hydrocarbons, it requires a system specifically designed around A3 refrigerant constraints.
R1270 profile →Water & Air
Specialist natural working fluidsWater (R718) and air (R729) are important to the broader natural-refrigerant concept but occupy specialist cycle and application niches rather than the mainstream roles served by R290, R744 or R717.
Browse refrigerant database →Natural refrigerants vs HFO / HFC refrigerants
The categories differ in origin, but both still require application-specific system engineering and regulation checks.
Natural Refrigerants
Naturally occurring working fluids such as hydrocarbons, CO₂ and ammonia. Many have very low GWP, but their safety and pressure characteristics vary widely.
HFO / HFC Refrigerants
Purpose-made fluorinated refrigerants include both legacy high-GWP options and newer lower-GWP HFO / HFC routes such as A2L blends.
Where natural refrigerants are used
This application map shows common market roles, not a universal approval list.
Domestic Refrigeration
Household refrigerators and freezers commonly use small-charge hydrocarbon systems.
R600aHeat Pumps
Natural routes vary from residential/monoblock concepts to industrial heat recovery.
R290 · R744 · R717 industrialCommercial Refrigeration
Purpose-designed hydrocarbon and CO₂ systems are important lower-GWP routes.
R290 · R744Cold Storage / Industrial
Large systems frequently use industrial natural-refrigerant architectures.
R717 · R744Transport Refrigeration
CO₂ and other application-specific routes appear depending on system design.
R744 · application-specificIndustrial Heat Pumps
Large heat-recovery and process-heat systems use specialist natural platforms.
R717 · R744Why natural refrigerants matter more in current HVAC/R transitions
Climate policy and equipment development are increasing interest in very-low-GWP system platforms, but natural refrigerants are one set of routes among several.
Very low direct GWP
R290, R600a, R744, R717 and R1270 all have very low GWP values on the reference basis used here.
HFC phasedown
Global HFC phasedown efforts and national/regional rules increase the value of technologies that avoid higher-GWP fluorinated refrigerants.
Equipment innovation
Advances in heat exchangers, controls, compressors and system architecture can expand where natural-refrigerant platforms are practical.
Natural refrigerants do not share one safety profile
Origin does not determine safety class. Hydrocarbons, CO₂ and ammonia require very different design strategies.
Pressure architecture matters
R744 has an A1 classification, but its high-pressure system architecture and thermodynamic behavior create major equipment-design considerations.
Flammability shapes the system
Hydrocarbon flammability influences refrigerant quantity, product architecture, standards and where equipment can be used.
Industrial site & materials context
Ammonia systems require careful attention to toxicity classification, site design, materials compatibility and industrial safety practices.
Natural refrigerants in global, U.S. and EU transition policy
Regulation can increase the relevance of natural-refrigerant equipment, but approval and market access remain application-specific.
Global HFC Phasedown
Kigali Amendment and broader HFC phasedown policy create demand for lower-GWP cooling technologies. They do not mandate one specific natural refrigerant for every application.
United States
EPA SNAP decisions are end-use specific. On the current residential/light-commercial AC and heat-pump table, R290 is listed with use conditions for self-contained room air conditioning; this should not be generalized to all split or heat-pump architectures.
European Union
Regulation (EU) 2024/573 progressively restricts fluorinated greenhouse gases by equipment category, capacity, GWP and date. This increases the strategic relevance of natural platforms, but does not require natural refrigerants everywhere.
Choose the system architecture before choosing the natural refrigerant
A natural-refrigerant decision starts with the application and operating requirements, not with the assumption that the lowest-GWP option must be selected.
Compare natural refrigerants with synthetic low-GWP routes
The tools help structure research and quantify climate metrics. They do not certify equipment compatibility or regulatory compliance.
Refrigerant Finder
Screen refrigerants by application, project type, safety context and GWP target.
Open Finder →Comparison Tool
Compare R290, R744, R717 and synthetic alternatives side by side.
Compare Refrigerants →GWP Calculator
Compare direct GWP values across refrigerant routes.
Calculate GWP →CO₂e Calculator
Estimate direct refrigerant CO₂-equivalent emissions from mass or leak scenarios.
Calculate CO₂e →Natural refrigerant questions
Direct answers to common questions about natural refrigerants, applications and safety.
What are natural refrigerants?
Natural refrigerants are naturally occurring substances used as refrigerants rather than purpose-made synthetic refrigerants. Major examples include hydrocarbons, CO₂ and ammonia.
Which refrigerants are natural?
Important examples include R290, R600a, R1270, R744 and R717, with water R718 and air R729 used in specialist applications.
Is R290 a natural refrigerant?
Yes. R290 is propane, a hydrocarbon refrigerant with GWP 3.3 and A3 classification.
Is R744 a natural refrigerant?
Yes. R744 is carbon dioxide, used in refrigeration, heat pumps, water heating and other specialist applications.
Is ammonia a natural refrigerant?
Yes. Ammonia is R717 and is widely used in industrial refrigeration and large heat-pump systems.
Are natural refrigerants safer?
Not automatically. R744 is A1, hydrocarbons such as R290 are A3, and R717 is B2L. Each requires different risk controls.
Are natural refrigerants more efficient?
Not universally. Efficiency depends on the refrigerant, system architecture, operating conditions, components and controls.
What is the lowest-GWP natural refrigerant?
Several major natural refrigerants have GWP around 1 on the reference basis used here, including R744 and R717, while R600a is also listed at 1. GWP alone does not determine suitability.
R290 vs R744: what is the main difference?
R290 is an A3 hydrocarbon used in purpose-designed systems, while R744 is A1 but requires high-pressure CO₂ system architecture.
R290 vs R32: natural vs A2L?
R290 is a natural A3 refrigerant with much lower GWP, while R32 is a synthetic A2L refrigerant with GWP 675. The correct route depends on equipment and application.
Which natural refrigerants are used in heat pumps?
R290 and R744 are important heat-pump routes, while R717 is used in industrial heat pumps.
Which natural refrigerant is used in household refrigerators?
R600a is widely used in domestic refrigerators and freezers.
Why is ammonia used in industrial refrigeration?
R717 is well established in large industrial refrigeration systems and can fit high-capacity cooling and heat-recovery architectures. Site and materials requirements are important.
Are natural refrigerants required in Europe?
Not as a blanket rule. EU F-gas restrictions increasingly limit fluorinated gases in specific equipment categories, which can favor natural platforms, but the legal result is category- and date-specific.
Authoritative sources behind this guide
Natural-refrigerant terminology, GWP values and regulatory statements should be checked against current authoritative references for the exact application.
Reference for the broad natural-refrigerant definition and the “natural five” categories: air, ammonia, carbon dioxide, hydrocarbons and water.
Open Guide →Reference basis used for R290, R600a, R744, R717 and R1270 GWP values on this page.
Open GWP Table →End-use-specific substitute listings, including the narrow R290 self-contained room AC use-condition context.
Open SNAP Table →Current F-gas framework with staged equipment restrictions that increase the relevance of very-low-GWP platform choices.
Open EUR-Lex →Start with the application, then compare the refrigerant architecture
Use the Finder and Comparison tools to screen natural and synthetic options, then verify equipment design, safety requirements and current regulations for the exact project.