R-290 vs R-32

What changes in the field

R-32 runs roughly twice the pressure of R-290. From the PT data, at 40°F evaporating R-32 reads 121.0 psig and R-290 63.9 psig. At 100°F condensing R-32 is 325.7 psig and R-290 173.9 psig. Both are single-component refrigerants with no glide, so each has one PT column.

The Section 608 class follows. At 104°F R-32 saturates at 359.4 psia, just over the 355 psia line, which makes R-32 equipment very high pressure under 40 CFR 82.152. R-290 saturates at 198.6 psia, high pressure. Either way the required recovery level for equipment under 200 lb is 0 in Hg, and Type II (or Universal) certification covers both; Type I covers factory-sealed units of 5 lb or less.

Flammability is the bigger difference. R-32 is A2L (mildly flammable, burning velocity 10 cm/s or less) and R-290 is A3 (highly flammable). Both need a recovery machine certified for flammable refrigerants under Appendix B4 of 40 CFR 82.158, and both come in gray RAL 7044 cylinders with a red band. R-290 is exempt from the venting prohibition only in the end uses listed in 40 CFR 82.154(a)(1), which include self-contained room AC; R-32 is never exempt. See flammability classes and recovery machine compatibility.

Retrofit or replacement

You cannot put R-290 in an R-32 system, or the reverse:

1. EPA’s SNAP listings for both are new equipment only. R-32 is acceptable subject to use conditions in new residential and light commercial AC and heat pumps (86 FR 24444, based on UL 60335-2-40). R-290 is acceptable only “for use in self-contained room air conditioning” (listed April 10 2015).
2. That means a US split-system heat pump or central AC cannot use R-290 at all under the current listings, retrofit or new.
3. The pressures, compressor and charge limits are different. A system built for one refrigerant is evaluated only for that refrigerant.

EPA proposed SNAP Rule 27 on Nov 10 2025, with a supplemental proposal on April 2 2026. It would update the use conditions for R-32, R-290 and six other refrigerants in residential and light commercial AC and heat pumps to the 4th edition of UL 60335-2-40 or to NRTL certification, for equipment made after a final rule. The updated listings would still be “acceptable only for use in new equipment specifically designed for the refrigerant.” It was not final at the time of review.

A failed R-32 system is repaired with R-32 or replaced. Compare with the other R-410A successors on R-410A vs R-32 and R-454B vs R-32.

Capacity, efficiency and cost

None of the manufacturer documents used here gives a capacity or efficiency comparison between R-290 and R-32 systems, so none is quoted. Danfoss gives R-290 roughly 90% of R-22’s volumetric capacity at 45°C (113°F) condensing, but that is a refrigerant property, not a system rating. Compare the AHRI ratings of actual units.

Both clear the Technology Transitions limit of 700 GWP for new residential and light commercial AC and heat pumps under 40 CFR 84.54. R-32 is an HFC with an AR4 GWP of 675, so its supply falls under the AIM Act phasedown. R-290 has no AR4 value (EPA uses 3.3 in 40 CFR 84.64) and is not a regulated HFC.

Charge sizes follow the safety standards rather than a fixed ratio, so use the nameplate. Danfoss puts hydrocarbon charges at about 40 to 45% of an equivalent HFC charge by mass in small hermetic systems.

Common questions

Is R-290 more efficient than R-32?

No source used here gives a verified system-level figure. Efficiency belongs to the matched equipment, so compare AHRI or ENERGY STAR ratings of the units you are choosing between.

Which is safer, R-32 or R-290?

R-32 is A2L and R-290 is A3 under ASHRAE 34; A3 is the more flammable class. In US residential AC, EPA lists R-290 only in self-contained room units, while R-32 is listed in split systems and heat pumps under UL 60335-2-40 use conditions.