Heat Pump Refrigerants: R290, R32 and the F-Gas Rules

Every heat pump contains a fluid that does the actual work of moving heat, and that fluid is called the refrigerant. In a heat pump cycle, the refrigerant absorbs heat from an external source such as air, ground, or water, causing it to evaporate into a gas, and it then releases that heat into your home as it condenses back to a liquid¹. The whole machine can be thought of as a refrigerator operating in reverse². Without the refrigerant, a heat pump is just a fan, a pump and some electronics.

Which refrigerant a heat pump uses has become one of the most consequential choices in the market, because the rules that govern fluorinated gases are now shaping what can be sold. From 2025, F gases with a global warming potential above 750 are banned in single split systems containing less than 3 kg of refrigerant³. The industry's response has been a shift to propane, R290, which has a global warming potential of 3⁴, while R32, with a GWP of 675⁵, remains in some systems, including high-temperature models⁶.

How the working fluid operates within the unit

The refrigerant is the heat transfer medium of the heat pump: the substance that carries warmth from outside into your radiators, underfloor pipes or hot water cylinder. In the cycle, the refrigerant absorbs heat from an external source such as air, ground, or water, causing it to evaporate into a gas; the compressor then raises its temperature and pressure, and when it condenses inside the heat exchanger it gives up that heat to the water circulating through your home¹. The device that does all this can be thought of as a refrigerator operating in reverse².

This is why heat pumps send water to pipes and radiators at a lower temperature than traditional gas or oil boilers⁹. The refrigerant's boiling point and pressure-temperature relationship set the physics: it evaporates at low temperature outside, even in winter, and condenses at a moderate temperature inside. The flow temperature the system delivers, and how efficiently it runs, is bound up with that refrigerant behaviour. With underfloor heating, the flow temperature could be lower compared with radiators, and this should result in the heat pump running much more efficiently⁹.

The quantity of refrigerant in a domestic unit is small, and in a monobloc it is sealed inside the outdoor unit at the factory. That matters for safety and for the rules, as later sections set out. What a householder needs to understand is that the refrigerant is not a fuel: it is not consumed, it is not burned, and in normal operation it simply circulates forever. It only leaves the system if the circuit is damaged or opened by an engineer.

Refrigerants used in British home heat pumps

Three refrigerants dominate domestic heat pumps in the UK: R290 (propane), R32, and the older HFCs such as R134a. Defra's consultation on the F-gas rules in Great Britain notes that R32 and R134a, two HFCs used in small heat pumps, have GWPs of 675 and 1430 respectively, and that the majority of hydronic monobloc heat pumps may use R290 (propane)⁵. So the market has already moved: the low-GWP propane units are the mainstream, and the HFCs are the legacy.

The product ranges bear this out. LG's Therma V R290 monobloc air source heat pump range uses the natural refrigerant R290 throughout, in a monobloc configuration⁴. Trianco's Activair Pro heat pump uses the natural refrigerant R290 with an ultra-low GWP of 3¹³. Viessmann's new residential air source heat pump launching at InstallerSHOW 2026 will use R290 refrigerant in its mainstream product¹⁴.

R32 has not disappeared. The Daikin Altherma 3 H HT heat pump, a high-temperature model, uses R32 refrigerant with a GWP of 675, and Daikin describes it as having a sealed refrigerant circuit in the outdoor unit⁶. R32 remains a legitimate choice where its properties suit the system design, particularly in high-temperature applications where the engineering demands are different.

The reasons propane is now standard for monobloc units

The shift to R290 is driven by the F-gas rules, and it has happened fastest in monobloc air-to-water heat pumps, the type most UK households now buy. Defra's assessment states that the majority of hydronic monobloc heat pumps may use R290 (propane)⁵. A monobloc keeps the entire refrigerant circuit sealed inside the outdoor unit, with only water piped between the unit and the house, which is what makes a flammable refrigerant practical in a domestic setting. Daikin makes the same point for its R32 model, describing a sealed refrigerant circuit in the outdoor unit with no risk of refrigerant leakage⁶.

The maker evidence is consistent across the market. LG's Therma V R290 monobloc air source heat pumps use natural refrigerant R290 with a GWP of 3, in a monobloc configuration⁴. Trianco's Activair Pro uses R290 with an ultra-low GWP of 3¹³. Viessmann's new residential launch for 2026 uses R290 in its mainstream product¹⁴. This is not one maker's preference; it is the direction of the whole market.

For the householder, the practical consequence is simple: if you buy a monobloc air-to-water heat pump today, it will almost certainly contain a small charge of propane. That has siting and safety implications, covered later, but it also means the climate performance of the refrigerant is close to irrelevant: a GWP of 3 means a full release of the charge would have a negligible warming effect compared with an HFC. The trade-off the makers have accepted is flammability, managed through design standards and installation clearances.

Global warming potential: the figure underpinning the regulations

Global warming potential, GWP, is the number that says how much heat a given mass of a gas traps in the atmosphere relative to the same mass of carbon dioxide. It is the single figure the F-gas rules are built on. The differences between refrigerants are large: R290 propane has a GWP of 3⁴, R32 has a GWP of 675, and the older HFC R134a has a GWP of 1430⁵. A kilogram of R134a released does over 400 times the climate damage of a kilogram of propane.

The reason the number matters is leakage. A heat pump's refrigerant charge is sealed, but circuits can be damaged, and when an HFC escapes it goes straight to the atmosphere as a potent greenhouse gas. The policy response is to push the market towards refrigerants whose escape barely matters. Government programmes now use the threshold directly: the Heat Pump Ready Programme Stream 2 Wave 2 projects work with low-GWP refrigerants, defined as below 150 GWP¹⁵. R290, at 3, clears that bar by a wide margin; R32, at 675, does not.

The revised European F-gas Regulation, adopted in 2024, uses GWP limits as prohibitions before the phase-out dates, including for stationary air-conditioning and heat pumps placed on the market¹⁶. The UK has its own version of these rules, as the next section explains, but the mechanism is the same: set a GWP ceiling, and anything above it cannot be placed on the market after a given date. That is why GWP, an abstract-sounding number, decides which heat pumps you can buy.

F-Gas regulations covering split and monobloc setups

The UK bans on F gases in new equipment work by GWP limit and by system type. From 2025, F gases with a global warming potential above 750 are banned in single split systems that contain less than 3 kg of refrigerant³. That threshold of 750 sits just above R32's 675, which is why R32 split systems have continued in use, and well below R134a's 1430, which is why that refrigerant has been pushed out of new small systems⁵.

For bigger equipment, the position is different. Official guidance states plainly: "There are no bans for larger air-conditioning or heat pump systems, eg chillers or larger split systems."³ The bans bite at the small, domestic end of the market first, which is exactly where the shift to R290 has happened. The revised European regulation points the same way, with prohibitions on placing products on the market, such as stationary air-conditioning and heat pumps, based on a GWP limit above 150 before the phase-out dates¹⁶.

The rules also reach into building standards. Scotland's Domestic Building Services Compliance Guide states that if installed in a new dwelling, heat pumps should use refrigerants complying with the provisions of current F-gas Regulations¹⁷. So the refrigerant choice is not only a market matter; it is written into what a compliant new-build installation must use.

Handling the refrigerant is itself a regulated activity. F-gas handling for stationary refrigeration, air-conditioning and heat pump equipment is a regulated profession in the UK, with City and Guilds among the qualifying bodies, and the UK recognises equivalent qualifications issued by an EU Member State⁸. In Great Britain the regulator is the Environment Agency, in Scotland it is the Scottish Environment Protection Agency, and in Northern Ireland it is the Northern Ireland Environment Agency⁸. So the F-Gas Regulation does apply in the UK after Brexit, under UK regulators with UK-recognised qualifications.

The outlook for existing heat pump installations

The bans are placing-on-the-market rules: they stop new equipment with high-GWP refrigerants being sold, and they do not order the removal of what is already on your wall. Official guidance confirms there are no bans for larger air-conditioning or heat pump systems, eg chillers or larger split systems³, and the prohibitions in the revised regulation are framed around products and equipment being placed on the market¹⁶. A heat pump legally installed before a ban date stays legal.

The phase-down works on supply rather than confiscation. HFCs remain available in shrinking quantities for servicing and repair, so an existing R32 or R134a system can still be maintained and refilled by a qualified engineer. What the phasedown changes over time is the cost and availability of those refrigerants, which is a pressure on the market rather than a cliff edge for householders.

Planning rights follow the same pattern of retention. Welsh Government guidance on changes to permitted development rights confirms that under existing permitted development rights a single heat pump on a block of flats is currently permitted, and this will be retained¹⁸. The wider permitted development rules for air source heat pumps also continue to apply, with limits such as no part of the heat pump being installed within 1 metre of the boundary of the curtilage of the dwellinghouse¹⁹, and caps on the number of units: not more than one on a dwellinghouse that is not detached or a block of flats, and not more than two on a detached dwellinghouse²⁰.

For an existing household, the practical reading is this: nothing in the F-gas rules forces you to replace a working heat pump, and nothing removes your right to have it repaired. The rules shape what is available when the time comes to replace it.

Maintenance, leak inspections and an engineer's typical work

There is no annual leak-testing obligation stated for a typical domestic monobloc in the guidance here. What the guidance does say, repeatedly, is that servicing is tied to your warranty. Energy Saving Trust notes that an annual service will help you identify any potential issues, and is often a condition of your heat pump warranty²¹. Government guidance on finding an installer says the same: regular servicing is often a requirement of guarantees and warranties²².

A service is a concrete list of tasks, not a vague check. It includes cleaning coils, cleaning fan blades, inspecting filters, checking refrigerant level and pressure, and checking that all electrical connections are safe²¹. The refrigerant check is part of that, so a yearly service is the practical leak check for most households. Energy Saving Trust's advice on efficient running adds a seasonal prompt: it is better to fix issues quickly and reduce the risk of your heat pump breaking down in winter²³.

What an owner receives is also defined. Welsh guidance on new dwellings states that operating and maintenance information provided to the dwelling owner should include details of the heat loss calculation, design flow temperature, competent person scheme confirmation, size of emitter circuit and minimum set back temperatures²⁴. That handover pack is the reference for what the system was designed to do.

Certification sits behind the equipment. Heat Pump KEYMARK certificates, such as the one issued for a NIBE F1x45 to F103x400 range, entitle the holder to use the mark of conformity in conjunction with the specified registration number, with testing to standards such as EN 16147:2011-04⁷. The point for a householder is that certified products have been independently tested, and the certificate is traceable.

Precautions required for flammable refrigerants

R290 is propane, which is flammable, and R32 is mildly flammable, so both are covered by a dedicated product safety standard: IEC 60335-2-40:2024, now in edition 8.0, published on 11 December 2024²⁵. The standard deals with the safety of electric heat pumps, sanitary hot water heat pumps and air conditioners, incorporating motor-compressors, as well as hydronic fan coil units, dehumidifiers, thermoelectric heat pumps and partial units²⁵. It covers appliances rated at not more than 300 V for single phase and 600 V for other appliances, including DC-supplied and battery-operated appliances²⁵.

The standard's refrigerant scope is explicit: it does not take into account refrigerants other than group A1, A2L, A2 and A3 as defined by ISO 817²⁵. Those groups are the flammability classes, from A1 (non-flammable) through A2L (mildly flammable, like R32) to A3 (higher flammability, like propane). Flammable refrigerants are limited to those of a molar mass of more than or equal to 42 kg/kmol based on the worst case formulation as specified in ISO 817²⁵. The standard also has limits: it does not specify the criteria to ensure competence of persons during installation, servicing and disposal, and safety requirements during disposal are not specified in this standard²⁵.

Installation practice is governed by the manufacturer's instructions. The Heat Pump Association UK's statement on R290 safety zones exists to explain that manufacturers' manuals may advise different approaches to mitigating possible risks from residential outdoor air-to-water heat pumps containing higher flammability refrigerants, and that installers, specifiers, designers and system owners and operators must follow manufacturer guidance²⁶. The statement is blunt on the point: "the manufacturer instructions must be strictly followed regarding requirements for safety-relevant minimum clearances and other mitigation measures intended to provide protection in the event of refrigerant leakage."²⁶

Behind the product standard sit the installation standards. The relevant British Standards include BS EN 378-3:2008 on refrigerating systems and heat pumps, safety and environmental requirements, installation site and personal protection; BS EN 15450:2007 on the design of heat pump heating systems; BS EN 805:2000 on water supply requirements for systems and components outside buildings; and BS 5930:1999 with Amendment 2:2010 on site investigations²⁷. CE and UKCA marking is mandatory for refrigeration, air conditioning and heat pump products²⁶. For householders, the takeaway is that a flammable-refrigerant heat pump is safe when installed to the maker's stated clearances by someone who knows the rules.

The practical consequences of a refrigerant leak

A refrigerant leak in a domestic heat pump is, first, a loss of heating: the system cannot move heat without its charge, so the practical effect is a heat pump that stops working or performs badly. That is why the servicing advice matters: fix issues quickly to reduce the risk of the heat pump breaking down in winter²³.

For R290 units, the safety design is built around the leak scenario. The Heat Pump Association UK's requirements state that "it must be ensured that in the event of a refrigerant leak, appropriate measures are put in place to reduce the risk of refrigerant entering the building through openings, vents, doors or similar pathways, and ensure that no people outdoors or in adjacent buildings are endangered."²⁶ That is what the minimum clearances in the installation manual are for: they keep the unit far enough from openings and boundaries that a leak disperses harmlessly outdoors.

For monoblocs, the design itself reduces the exposure. Daikin describes its outdoor unit as having a sealed refrigerant circuit with no risk of refrigerant leakage⁶, and the whole monobloc concept keeps the refrigerant outside the dwelling, with only water pipes passing through the wall. Refrigerant pipework for heat pumps in dwellings should be fully insulated²⁴, which applies to the water side of a monobloc and to any refrigerant lines in split systems.

If a leak does occur, the response is an engineer's job, not a householder's. Work on the refrigerant circuit must be carried out by a qualified F-gas handler, a regulated profession in the UK⁸. A householder's role is to notice the symptoms, poor heating performance or an error on the unit, and to call for service rather than open anything.

How refrigerant selection affects a home's energy self sufficiency

A heat pump replaces delivered fuel with electricity, and the Renewable Energy Association notes that this eliminates the need for fuel deliveries required by other types of domestic heating². That is the core independence gain: no oil tanker, no LPG bottle, no gas grid dependence for the heat itself. The refrigerant is part of that story, because a low-GWP charge means the environmental case for the system does not rest on the charge never escaping.

The remaining dependence is the electricity supply. Government modelling of heat pump savings uses a standard 3-bedroom detached house with good insulation, a heat pump with typical efficiency, a smart electricity tariff enabled by a smart meter, gas standing charges removed in the heat pump scenario, and a fully electric home with no gas used for cooking in either scenario²⁸. The savings case is therefore tied to tariffs and meters, not just the hardware: a household that wants independence pairs the heat pump with a smart meter and, ideally, generation of its own.

Refrigerant development is also an economic issue for households. The government's heat and buildings analysis identifies low global warming potential refrigerants that can allow high efficiencies at high temperatures, above 60°C, as a research and innovation need, and notes that running cost makes up 55 to 65% of total heat pump lifecycle cost²⁹. Better refrigerants at higher temperatures widen the range of homes heat pumps can serve without emitter upgrades, which lowers the barrier for ordinary households.

The international effort is coordinated: the Heat Pumping Technologies programme runs Annex 54, Heat pump systems with low Global Warming Potential (GWP) refrigerants, an international collaboration project that began in 2019¹⁶. For the householder, the direction of travel is clear and stable: the refrigerant in your next heat pump will be low-GWP, most likely propane in a sealed outdoor unit, governed by product safety standards and handled only by certified engineers. The system itself, once installed, is yours: it needs no fuel deliveries, and its climate and safety performance no longer depends on a gas that does damage if it escapes.