Understanding the gas absorption heat pump (GAHP) without selling it as a mass-market solution
How it works: gas absorption vs electric compression (what changes on site)
A gas absorption heat pump does not compress a refrigerant using an electric compressor. The cycle is driven by a gas burner that regenerates an absorbent solution (often NH3/H2O). On site, that translates into low electrical current draw (pumps, fans), but a genuine “boiler-world” approach you must integrate. Plan for flue gas evacuation, combustion air supply, combustion tuning, and dedicated maintenance.
The main families of gas absorption heat pumps: air-to-water GAHP and water-to-water GAHP, and their limits
In practice you mostly come across air-to-water GAHPs in tertiary buildings or multi-family plant rooms. Water-to-water GAHPs target tempered water loops, geothermal sources or groundwater. Their value shows up when you must maintain higher operating temperatures on an existing network, with performance expressed on LHV. In single-family homes, footprint, cost, service ecosystem and gas availability heavily limit relevance.
What the client means by “gas heat pump”: clear up confusion from the quote stage
On your quote, name the technology clearly. A GAHP is neither an electric heat pump, nor a hybrid heat pump (electric heat pump + boiler backup). State main energy source, generator type, useful output, LHV efficiency, flue constraints and hydraulic constraints. You avoid apples-to-oranges comparisons and disputes at handover.
LHV efficiency: how to read gas absorption heat pump figures
LHV efficiency, “gas COP” and seasonal performance: practical definitions for installers
On a gas absorption heat pump, “LHV efficiency” expresses the useful heat delivered to the distribution system divided by the gas energy consumed, calculated on the Lower Heating Value. Depending on the manufacturer, the figure may be presented as a “gas COP” or a gas utilisation efficiency (e.g. GUE). Always check whether auxiliary electricity (pump, fan) is included, and under which hydraulic operating temperatures the value is stated.
What makes efficiency vary: flow temperature, high-temperature operation, defrost cycles, hydraulics
Efficiency drops as flow temperature rises, especially on existing high-temperature networks. Add defrost cycles in air-source applications and losses linked to poorly set-up hydraulics. On site, record flow, return, flow rate and ΔT, then reset the weather compensation curve and balancing. An oversized circulator can “eat up” the gains shown on the datasheet.
2026 watch points: measurements, manufacturer documentation and test conditions to verify
In 2026, never compare two units without aligning the test conditions. Ask for the referenced test standard, air and water temperatures, and the mode (space heating only, with DHW, with auxiliaries). In the quote and site file, document the intended operating temperatures, measurement points, and energy metering (gas and auxiliary kWh) that will be used for set-up and verification.
Use cases where a gas heat pump still makes sense: tertiary, multi-family, existing networks
Tertiary buildings (offices, retail): simultaneous demand, power constraints and continuity of service
In tertiary buildings, the gas absorption heat pump makes sense when you need high thermal output with limited electrical demand, while keeping headroom for continuity of service. It integrates well on long operating hours under BMS control, with a boiler for peak load and redundancy. It is comfortable where space heating and hot water overlap, and where an electrical upgrade is undesirable.
Multi-family: central plant room, optimising what’s there, and cascade control
In multi-family, it slots into a central plant room as a pre-heating stage, with a cascade logic of GAHPs plus existing boilers. You keep the hydraulics, optimise runtime hours, and control on flow and return temperatures to maximise the “heat pump” share without upsetting system balancing.
Existing high-temperature networks: retrofitting without replacing every heat emitter (and how far that’s true)
On high-temperature networks, it helps when you cannot replace every heat emitter. But it is not magic. The higher the flow setpoint stays, the more the gain erodes. Frame the project with weather compensation data, real delta T and controls. Beyond that, lowering the operating temperatures or partially replacing emitters becomes unavoidable.
Why gas absorption heat pumps remain niche in single-family homes
Cost, footprint, servicing: when electric (air-to-water) is still easier to sell and install
In homes, the gas absorption heat pump first runs into market reality. A narrower manufacturer offering, parts lead times, and an equipment price often higher than an air-to-water heat pump. On installation you stack hydraulics with “boiler-world” requirements (flue, gas), with more demanding servicing and fewer trained technicians. As a result, it is harder to justify versus an electric solution that has become the default.
Installation constraints: ventilation, flue, gas supply, noise and outdoor siting
The job requires a correctly sized gas supply, a compliant flue gas evacuation route, and verification of ventilated volumes. Add outdoor siting constraints (footprint, access, clearances) and acoustic treatment. On tight plots, these points can quickly kill feasibility.
Payback and usage: house profiles where it doesn’t work (and the rare exceptions)
Where electricity is available and emitters are already low-temperature, an air-to-water heat pump keeps the edge on seasonal performance and simplicity. The gas option only rarely makes sense—mainly when an existing high-temperature radiator circuit must be retained and gas is already on site, or when an electrical constraint blocks the project. Otherwise, the extra cost is hard to absorb, notably depending on the choice between low-temperature and high-temperature heat pumps on the emitter side.
Grants, VAT and commercial positioning in 2026: securing your files without risky promises
National schemes: what you can say (and what you must avoid) depending on the job type
In 2026, under MaPrimeRénov’ “per measure”, MaPrimeRénov’ is limited to air-to-water or ground-source heat pumps, connection to a district heating network, and removal of an oil tank. For anything else, be explicit. Either the job qualifies for the accompanied pathway, or you stick to CEE. On the tax side, air-to-air heat pumps are at 5.5% since 18/07/2026. Gas or oil-fired generators remain at 20%.
CEE: habits to price correctly and avoid prohibited combinations depending on the measures
- Lock in the CEE sheet from the technical visit. Measurements, areas, R-values, thicknesses, output—everything must be traceable.
- Get the CEE commitment signed at the right time. A file started too early will fail at audit.
- For measures no longer eligible “per measure”, never sell a “bundle of MaPrimeRénov’ on top of the CEE premium” on top of the CEE premium.
Straight talk: when to propose a GAHP, and when to steer towards air-to-water, biomass or district heating
A gas absorption heat pump mainly makes sense in tertiary or multi-family applications, with an existing high-temperature network and electrical constraints. In single-family homes, it remains a niche. If the file targets national subsidies, steer instead towards an air-to-water heat pump, district heating connection, or biomass depending on the scope of works and site constraints.
