Convert R-1234ze to CO2e
| kg R-1234ze | kg CO₂e |
|---|---|
| 0.5 | 0.685 |
| 1 | 1.37 |
| 1.5 | 2.055 |
| 2 | 2.74 |
| 3 | 4.11 |
| 5 | 6.85 |
| 10 | 13.7 |
| 20 | 27.4 |
| 50 | 68.5 |
| 100 | 137 |
Each row uses the same factor as the converter above: 1 kg R-1234ze = 1.37 kg CO₂e.
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R-1234ze — HFO-1234ze(E), trans-1,3,3,3-tetrafluoropropene — is a low-GWP hydrofluoroolefin used in chillers, heat pumps and foam blowing, and the quiet low-GWP half of the blends R-450A and R-515B. Its global warming potential is often printed as 7, but that is a regulatory nameplate figure, not the science. The current IPCC value is 1.37, and this converter uses it. The gap between the two — and why R-1234ze is still not “zero” the way ammonia or propane are — is explained below.
To convert R-1234ze to CO2e, multiply the mass by its GWP-100 of 1.37 (IPCC AR6). So 1 kg R-1234ze ≈ 1.37 kg CO2e — close to parity with its own mass. The widely-quoted 7 is the older EPA SNAP / regulatory nameplate value, not the current IPCC assessment.
The same refrigerant is quoted with two different global warming potentials; only one is the current basis for a greenhouse-gas inventory:
| GWP-100 | Basis | Use for |
|---|---|---|
| 1.37 | IPCC AR6 (current) | Greenhouse-gas inventories — this converter |
| 7 | EPA SNAP / regulatory nameplate | Only where a rule specifically requires it |
The 7 on equipment and in some regulations is the EPA SNAP figure, not an IPCC assessment value (AR4 predates the compound). The current IPCC AR6 GWP-100 is 1.37.
The reason 1.37 is right and 7 is legacy comes down to atmospheric lifetime. R-1234ze(E) is an unsaturated olefin — it has a reactive double bond that lets it break down in the lower atmosphere in about 16 days, versus roughly 14 years for the R-134a it replaces. It simply never stays aloft long enough to trap much heat. The “7” predates the settled IPCC AR6 assessment and lingers on equipment plates and in some regulatory tables.
How to convert R-1234ze to CO2e
Carbon-dioxide-equivalent multiplies a gas’s mass by its global warming potential. R-1234ze’s GWP-100 is 1.37, so the CO2e figure is only fractionally larger than the mass leaked.
kg CO2e = kg R-1234ze × 1.37
The value resolves live from MasterBrain. R-1234ze postdates the AR4 and AR5 assessments, so only the AR6 basis is stored and there is no vintage toggle; the provenance line beneath the converter shows the AR6 source.
Converting back
To go from a CO2e figure to a mass of refrigerant, divide by the GWP-100: kg R-1234ze = kg CO2e ÷ 1.37. Use the swap control on the converter to reverse the direction.
For scale: a 100 kg charge of R-1234ze leaking entirely is about 137 kg CO2e. The same 100 kg of R-134a would be roughly 153,000 kg CO2e — more than a thousand times higher. That ratio is the whole reason chiller manufacturers moved to R-1234ze and its blends.
Why R-1234ze’s GWP is low — but not zero
R-1234ze earns a low global warming potential because it is a short-lived hydrofluoroolefin, removed from the atmosphere within weeks rather than persisting for years. But unlike the natural refrigerants ammonia (R-717) and propane (R-290), it is still a fluorinated compound, and its 1.37 is a genuine — if small — direct warming effect. It is “low-GWP”, not “no-GWP”.
The two automotive/chiller HFOs are often confused. R-1234yf (GWP ≈ 0.5) is the one that replaced R-134a in car air-conditioning. R-1234ze(E) (GWP 1.37) is its isomer — same formula, different structure — used mostly in commercial chillers, heat pumps and foam. Their GWPs differ, so a converter must use the right one.
The blends R-1234ze hides inside
Much of R-1234ze’s real-world use is not as a pure refrigerant but as the low-GWP dilutant in fluorinated blends designed to drop the GWP of an R-134a system without a full redesign:
- R-450A — 42% R-134a / 58% R-1234ze(E) by mass. GWP-100 ≈ 643. A lower-GWP, non-flammable (A1) drop-in for R-134a in medium-temperature commercial refrigeration and chillers.
- R-515B — 8.9% R-227ea / 91.1% R-1234ze(E), an azeotrope. GWP-100 ≈ 322. An A1 replacement for R-134a in new centrifugal and positive-displacement chillers.
Because R-1234ze is already near-zero in warming terms, correcting it from 7 to 1.37 barely moved these blends — almost all of each blend’s GWP comes from its R-134a or R-227ea partner, not the R-1234ze.
Flammability and where it fits
Pure R-1234ze(E) is classified A2L — mildly flammable, low toxicity — although it is difficult to ignite and is non-flammable at typical ambient temperatures. That mild-flammability rating is why it is often deployed as part of a non-flammable A1 blend (R-450A, R-515B) rather than neat, and why safety standards govern charge sizes for the pure fluid. It is not a like-for-like drop-in for every R-134a system.
Where R-1234ze is used
- Commercial chillers — centrifugal and screw chillers for district cooling and large buildings, replacing R-134a.
- Heat pumps — medium- and high-temperature industrial heat pumps.
- Foam blowing and aerosols — a low-GWP blowing agent for insulation foam and a propellant in technical aerosols.
- Blend feedstock — the low-GWP constituent of R-450A and R-515B.
- Scope 1 fugitive emissions — an R-1234ze charge is reported at 1.37 kg CO2e per kg leaked; the system’s energy use is usually the larger line.
Building a refrigerant inventory that mixes HFOs, HFC blends and natural refrigerants, and want the leak emissions handled across many systems at once?
Frequently Asked Questions
Multiply the mass by its GWP-100 of 1.37 (IPCC AR6). For example, 50 kg R-1234ze × 1.37 = 68.5 kg CO2e. To reverse, divide by 1.37.
The IPCC AR6 100-year GWP is 1.37. It is low because R-1234ze(E) is a short-lived hydrofluoroolefin that breaks down in the atmosphere within about 16 days. You will also see 7 quoted — that is the older EPA SNAP / regulatory nameplate value, not the current IPCC figure.
7 is a regulatory nameplate value used in some EPA SNAP and equipment documentation. The settled IPCC AR6 assessment puts the 100-year GWP at 1.37. For a greenhouse-gas inventory, use 1.37; only use 7 where a specific rule explicitly requires that figure.
They are structural isomers — the same chemical formula arranged differently. R-1234yf (GWP ≈ 0.5) replaced R-134a in car air-conditioning. R-1234ze(E) (GWP 1.37) is used mainly in commercial chillers, heat pumps and foam blowing. Because their GWPs differ, they convert to CO2e with different factors.
R-1234ze(E) is the main low-GWP constituent of R-450A (42% R-134a / 58% R-1234ze, GWP ≈ 643) and R-515B (8.9% R-227ea / 91.1% R-1234ze, GWP ≈ 322). Both are non-flammable (A1) replacements for R-134a in refrigeration and chillers.
Pure R-1234ze(E) is classified A2L — mildly flammable and low toxicity — though it is hard to ignite and non-flammable at ordinary ambient temperatures. It is frequently used inside non-flammable A1 blends (R-450A, R-515B) rather than neat, and charge limits apply to the pure fluid.
Divide by the GWP-100: kg R-1234ze = kg CO2e ÷ 1.37. For example, 137 kg CO2e ÷ 1.37 = 100 kg R-1234ze. Use the swap control on the converter to reverse direction.