Heat-pump compressor cut-off temperatures and refrigerants on the certified list

The listed lower cut-off is the air temperature below which a heat pump’s compressor stops and its backup heat takes over. Of the 90 heat-pump rating sets that report a single value, 76 list 35 to 45 °F; the CO2 units go down to −26 °F.

What the field says

The ENERGY STAR listing has a column for the lowest temperature at which the compressor still runs. It describes the heat pump’s operating range as reported by the partner. It is not part of the UEF test, which runs at fixed lab conditions.

Refrigerants on the list

R-134a is the most common refrigerant by far, with 452 of the 609 heat-pump model numbers. CO2 (R-744) follows with 94, all of them split systems. R-1234yf, R-513A and R-32 make up the rest.

The distribution

The most common listed value is 35 °F, on 29 sets. The lowest, −26 °F, belongs to SanCO2 GS5-45HPC HP + ECO-119GLBK and SanCO2 GS5-45HPC HP + ECO-83SSAQB. Among the CO2 sets, only 4 of 10 report a usable single value, between −26 and −13 °F.

The gap in the data

Many listings carry “1 °F” in this field, which also appears as a placeholder in other columns of the same dataset. We treat it as missing. It sits mostly on the CO2 split systems listed by the A.O. Smith Corporation, so the CO2 figures above rest on the SanCO2 and Reclaim Energy listings. In all, 11 of the 101 heat-pump sets have no single usable cut-off, either because of that rule or because their model numbers list different values.

Cut-off by heat-pump type

The subtype explains most of the spread. The 71 integrated 240-volt sets with a usable value list 23 to 45 °F, with a median of 37 °F. The 9 plug-in sets sit in a narrow band, 35 to 37 °F. The 10 split systems are a different world: −26 to 5 °F, every one of them below the lowest integrated tank.

The coldest listings

The coldest integrated tank on the list is LG APHWC501D, listed at 23 °F. Below that point only split systems remain, 10 sets in all, from the coldest up: SanCO2 GS5-45HPC HP + ECO-119GLBK (−26 °F), SanCO2 GS5-45HPC HP + ECO-83SSAQB (−26 °F), Smart Solar SSG2-ES 120 (−20 °F), Smart Solar SSG2-ES 65 (−20 °F), Smart Solar SSG2-ES 80 (−20 °F), Reclaim Energy MP120F-RC (−13 °F), Reclaim Energy MP80F-RC (−13 °F), Eco-Logical OMNI-50HP1-1A (5 °F), Eco-Logical OMNI-50HP2-1A (5 °F) and Eco-Logical OMNI-80HP2-1A (5 °F). No integrated tank, whether 240-volt or plug-in, is listed below 23 °F, so the colder end of the range belongs entirely to units whose compressor sits outside the tank.

What “not listed” means on this site

Type and maker pages show “not listed” in the cut-off column when a set has no usable single value. That covers three cases: the field is empty in the source, it holds the 1 °F placeholder, or the model numbers in one set report different values. The pages never fill the gap with an estimate, and a set without a value is simply left out of the cut-off charts and counts, which is why the totals here are smaller than the number of heat-pump sets.

Refrigerants by year of certification

Most heat-pump listings carry a certification date in 2025 or 2026. Of the 364 heat-pump model numbers certified in 2026, 250 use R-134a, 88 CO2, 20 R-1234yf and 6 R-513A. All 30 R-513A model numbers were certified in 2025 or 2026, and the 2 R-32 models in 2025. The dates are certification dates, which change when a partner recertifies, so they show when a listing was last confirmed rather than when a model first appeared.

How to read it

• A cut-off is a listed operating limit, not a test result, and the site compares it only between heat pumps.
• A lower cut-off means the compressor is listed as running in colder air; the listing does not say how efficient it is at that temperature.
• The site gives no climate advice and does not match cut-offs to places.

Each heat-pump page shows the cut-off of every set in its table, and the split-system page plots them against the rest of the list.