EnergyAE / Knowledge Base

HFO R-1234yf

Pros and cons of R-1234yf (HFO) as a refrigerant for heat pump water heaters.

R-1234yf (2,3,3,3-tetrafluoroprop-1-ene) is a hydrofluoroolefin (HFO) refrigerant developed as a low-GWP replacement for R-134a. It is widely used in automotive air conditioning and is increasingly appearing in residential heat pump applications.

GWP4
ODP0
FlammabilityA2L (mildly flammable)
Max outlet temperature~70–75 °C
Cycle typeSubcritical
Operating pressureModerate (similar to R-134a)

Pros

  1. Very low GWP: At a GWP of 4, R-1234yf is dramatically better than the refrigerants it replaces — R-134a (GWP 1430) and R-410A (GWP 2088) — while remaining a synthetic option where CO₂ or R-290 are not practical.
  2. Moderate operating pressure: Unlike CO₂, R-1234yf operates at moderate pressures in a conventional subcritical cycle. This means standard compressor and pipework designs can be used, keeping system costs down.
  3. Drop-in compatibility: R-1234yf is close to R-134a in thermodynamic behaviour, making it a practical retrofit or direct replacement in system designs previously built around R-134a.
  4. Non-ozone depleting: Zero ozone depletion potential (ODP = 0).
  5. Good residential temperature range: With a maximum outlet of around 70–75 °C, R-1234yf covers most residential domestic hot water applications comfortably.

Cons

  1. Mildly flammable (A2L): R-1234yf is classified A2L — mildly flammable under certain conditions. While less of a concern than R-290 (A3), it still requires compliance with flammability safety standards in system design and installation.
  2. Higher cost than alternatives: R-1234yf is produced under patent by Honeywell and Chemours, which limits competition and keeps prices elevated compared to R-290 or R-134a.
  3. Not a natural refrigerant: Unlike CO₂ or R-290, R-1234yf is a synthetic compound. Its production relies on petrochemical feedstocks.
  4. TFA breakdown product: When R-1234yf degrades in the atmosphere it produces trifluoroacetic acid (TFA), a persistent environmental contaminant. Regulatory scrutiny of TFA is increasing, creating some uncertainty about the long-term status of HFOs.
  5. Temperature ceiling: The ~75 °C output limit is adequate for most residential applications but rules out high-temperature industrial or commercial uses where CO₂ (up to 90 °C) is the better choice.