Refrigerant GWP explained: a ratio, not a product rating

Global warming potential compares one gas against carbon dioxide. It states how much warming a kilogram of that gas causes over a stated period, set beside a kilogram of carbon dioxide across the same period. Carbon dioxide is the thing being divided by, so it sits at 1 in every published table.

A ratio behaves nothing like a rating. A rating implies a scale somebody designed, with a floor, a ceiling and a good end to aim at. This has none of those. It is arithmetic performed on a physical property, and it climbs as far as the chemistry carries it.

The figure is silent on most of what a buyer cares about. Flammability and toxicity are graded separately, in a safety class of their own. Nothing in the number describes how well the gas cools, what pressure it works at, or how much of it a system holds. Ozone depletion is a third index again, measuring a different harm entirely.

One distinction underpins everything that follows. GWP is a property of the substance, not of the machine on your ledge. A charge sealed inside a working circuit emits nothing at all, whatever its number happens to be. What converts the ratio into an actual emission is the mass that gets out.

Every GWP is quoted over a stated number of years, and changing the years changes the answer. Take R32, listed in the assessment reports as HFC-32 and fitted to most new household splits sold here. The IPCC Sixth Assessment Report gives it 2,690 over 20 years, 771 over 100 years, and 220 over 500 years. One gas, one report, three answers.

That spread comes out of how long each gas survives up there. The same report puts R32's atmospheric lifetime at 5.4 years. Carbon dioxide is the yardstick, and a large share of any carbon dioxide release is still working centuries afterwards. Over a short window the fluorinated gas is mostly still present, so the ratio runs high. Widen the window and it has long since broken down while the denominator carries on, so the ratio collapses.

Picking the window is a choice about what to weigh, not a fact anybody found. Singapore settles that choice in law. Its Environmental Protection and Management Act 1999 defines the term on a 100-year basis. One kilogram of a gas is set against one kilogram of carbon dioxide, using values NEA publishes.

Assessment reports move the numbers as well. The Fifth Assessment Report puts R32 at 677 over 100 years. The Sixth puts the same molecule at 771 over that same 100 years. Nothing about the gas changed between those publications. The measurement of it did.

That gap is not academic here, and the next section explains why. 771 sits above the ceiling written for household aircon. 677 sits below it. NEA states that the GWP values it works from are aligned with the Fifth Assessment Report, and the statute points at the list the agency publishes. Two accurate sources can disagree by roughly a hundred points. Only one of those figures decides what may be supplied here.

From 1 October 2022, a household aircon may not be supplied in Singapore if its refrigerant carries a GWP above 750. That restriction lives in the same Act, and it binds importers, manufacturers and sellers rather than owners. Supplying a regulated good that fails the requirement is an offence, carrying a fine of up to $10,000 on conviction.

The ceiling reaches a defined class of machine, not a brand or a price band. NEA writes a household air-conditioner here as a room air-conditioner that is single-phase and non-ducted, rated at 17.6 kW of cooling or lower, with variable refrigerant flow equipment left out. Ordinary household splits sit well inside that.

750 is not a national figure either. It is written per category, and the categories diverge sharply. A household refrigerator sits at 15 under the same scheme. So does an electrically driven water-cooled chiller of 1,055 kW or more that helps cool a building. The number follows what the equipment is and how much gas it carries.

Nothing about the rule looks backwards. NEA is explicit that the restriction reaches new sale or supply from that date onward, and that equipment already sold or installed beforehand is untouched by it. Suppliers were given until 30 September 2023 to clear non-compliant stock already in the country. No owner picked up a duty the morning it commenced.

A ceiling written as a number erases everything above it from new supply. Manufacturers do not argue with a threshold. They withdraw the ranges that fail and engineer around whatever clears, because no third option exists. A shopper met all of that as a changed model line and an unfamiliar sticker, with no visible connection to a figure in a government table.

The ratio accounts for what escapes, never for what the system consumes. A split system in a Singapore flat runs across a large share of the year, and the electricity behind that is a continuing cost for the whole service life. Refrigerant is a stock that only counts once it leaves the circuit. Which of the two ends up larger depends on how much gas gets out and how much power the machine draws.

The escaped weight is the term almost nobody quotes. GWP is stated per kilogram, so the real emission is leaked weight multiplied by the ratio. A circuit that holds its charge and is then emptied into a recovery cylinder has released close to nothing. That same system, losing gas yearly and vented on removal day, has released its charge several times over. Where an old charge ends up once a system leaves is covered separately.

Push back when a low GWP figure is offered as the environmental case for a purchase. It is one input, it has already been constrained by law, and every model lawfully in front of you cleared the identical bar. What still separates two machines is the efficiency figure under the tick band, capacity matched honestly to the room, and an installation tight enough not to leak.

Replacement is the argument to watch for, and none of this supports it. Building and disposing of a system carries its own cost, and the charge in the old one is released only if somebody chooses to release it. Nothing in the ceiling asks an owner to do anything. Anybody using it to press for replacing a machine that still cools has travelled well past what the rule says.

For a purchase today the question has largely been answered before you walk in. Every household split that may lawfully be sold here sits under 750, so the gas is not a lever anybody pulls between two compliant models. Which gas a particular system can physically take is a separate question, answered elsewhere on this site.

Read GWP as a supply signal rather than a product feature. A gas sitting well above the current ceiling is one whose new production is being squeezed by international agreement, and squeezed production surfaces as price and waiting time on a refill. That reaches an owner at exactly one moment: the day a sealed circuit gets opened and filled again.

Holding a system on a heavier gas is not a problem waiting on a schedule. A charge sealed inside a circuit is being emitted by nobody, and swapping out a working machine to change the gas inside it carries costs of its own. What genuinely shifts is the arithmetic on one particular fault. Once the circuit needs refilling, the gas going back in comes from a supply that keeps shrinking.

Ask which refrigerant the model uses, then ask for its number and where the number came from. A seller who names the gas, states the GWP and can say which assessment report and which window produced it is describing something checkable. A figure quoted with no report and no horizon behind it has not been sourced, and there is nothing there to verify.

• •Ask which assessment report a quoted figure came from. The Fifth and the Sixth disagree about the same molecules, and only one of them governs supply here.
• •Ask over how many years. A 20-year figure and a 100-year figure for one gas can differ by more than threefold.
• •Treat compliance as an entry condition rather than a distinction. Every new household split on sale here already sits under the ceiling.
• •Ask what the system holds in kilograms, not only what gas it holds. The ratio is per kilogram, so the charge weight is half the answer.
• •On an installed system, keep the attention on whether the circuit is tight. A charge that never escapes never becomes an emission.