LCA: Heat Pump vs Gas Boiler — Which Is Greener in 2026?

Understanding LCA: what you need to measure before comparing a heat pump and a boiler

LCA, emissions, primary energy: concepts to clarify on site

An LCA (life-cycle assessment) adds up a piece of equipment's impacts over its entire life cycle, most often in kg CO₂e. On site, check that you're comparing the same unit (final or primary kWh) and the same service delivered (heating only, or heating plus hot water). Note the annual heating need, the emitters, the setpoint, and the climate zone. Without these reference points, two studies can reach opposite conclusions for the same building.

Study boundaries: manufacturing, transport, use, end of life

Two LCAs can reach opposite conclusions if the scope changes. Make sure the analysis clearly includes:

• manufacturing of the generator, and for a heat pump, the refrigerant
• transport, installation, accessories (hot water tank, controls)
• consumption in use, backup heating, any leaks
• maintenance, replacements, recycling at end of life

The data that changes the result: the 2026 electricity mix, real-world efficiency, maintenance

In 2026, the carbon content of electricity depends on the generation mix and the time of consumption. The reference emission factors come from ADEME's Base Empreinte® (ADEME being France's environment and energy management agency). For electric heating, two values coexist: the annual average (≈ 52 gCO₂e/kWh) and the seasonalised "heating use" factor (≈ 79 gCO₂e/kWh), which better reflects the mix called on in winter. On site, use the actual SCOP (defrost cycles, flow temperatures), the boiler's real-world efficiency, and maintenance. To go further, see real-world heat pump performance.

LCA of a heat pump: where does the environmental impact actually come from?

Manufacturing and metals: the weight of hardware in the LCA

In an LCA, manufacturing weighs in mainly through the extraction and processing of materials. A heat pump packs a compressor, heat exchangers, and electronics. The heaviest contributors are copper, aluminium, and steel, plus logistics and assembly. Available FDES and PEP environmental declarations for residential air/water heat pumps converge around 1 to 2 t CO₂e for manufacturing an 8–12 kW unit. This is also where choosing robust, repairable, correctly sized equipment avoids paying for the impact twice.

Use phase: electricity consumption, SCOP, and emission factor

In use, the impact depends on the kWh consumed and the electricity mix. Seasonal SCOP varies with outdoor temperature, heating flow temperature, defrost cycles, and settings. For a typical heating need of 13,500 kWh/year, a heat pump with a SCOP of 2.5 (a conservative retrofit value) consumes around 5,400 kWh/year of electricity, i.e. 5 to 9 t CO₂e over 20 years depending on the factor used (ADEME's annual average or heating-use factor). A well-insulated house, low-temperature emitters, and careful control reduce consumption — and therefore impact — without changing the machine.

Refrigerant: R32, R290 (propane), and best practices

The refrigerant is a sensitive point because some have a high global-warming potential. R32 heat pumps (GWP 675) remain the market standard; the newer R290 (propane, GWP 3) generation reduces the refrigerant's contribution to the LCA to almost zero. Leaks are limited by clean commissioning, careful fittings, recovery at end of life, and compliance with the leak-tightness checks required under the F-Gas regulation. Installation quality directly determines the refrigerant's share of the overall footprint.

LCA of a gas boiler: which factors weigh most on the environment?

Combustion and direct emissions: CO₂, NOx, and combustion settings

In an LCA, the number-one contributor remains the use phase. Every kWh NCV of natural gas burned emits 0.205 kg CO₂e (combustion only, ADEME Base Empreinte). And if the boiler is poorly tuned or dirty, consumption rises. NOx mainly affects air quality. Fine tuning, proper flue evacuation, and a real-world efficiency close to nominal limit excess emissions.

Upstream gas: extraction, transport, and methane leaks in the LCA

Before it reaches the burner, gas already has an energy history. Extraction, processing, compression, sometimes LNG, and transport all weigh in the LCA. The sensitive point is methane leaks. According to the IPCC AR6, fossil methane has a GWP100 of 29.8 (and a GWP20 of 82.5, more relevant for a short decarbonisation horizon). Including the upstream, Base Empreinte gives ≈ 0.227 kg CO₂e/kWh NCV for natural gas, i.e. +11% compared with combustion alone.

Lifespan, maintenance, and replacement: the hidden impact over 15–20 years

Over 15 to 20 years, the impact isn't limited to the new appliance. Maintenance visits, replaced parts (circulator pump, sensor, expansion vessel), and end of life all add up. Annual servicing limits breakdowns and avoids the excess consumption that drags down the overall impact.

Comparing heat pump and boiler with a useful LCA: a simple method for choosing by dwelling

Assumptions used for the "Key figures" block

The orders of magnitude shown on this page rest on the following assumptions, to be adapted to the real case: heating need of 13,500 kWh/year, 20-year lifespan, 2024 Base Empreinte® ADEME emission factors (electricity, heating use: 79 gCO₂e/kWh; natural gas, NCV including upstream: 227 gCO₂e/kWh), retrofit SCOP of 2.5 (air/water heat pump with high-temperature radiators) to 3.5 (heat pump on underfloor heating in an insulated building), boiler efficiency from THPE (very-high-performance) to standard, 75–95%. Methodological source: Base Empreinte® ADEME.

Partial vs whole-house renovation: when insulation changes everything in the LCA

In a partial renovation, the LCA is driven by the use phase. If the dwelling remains an energy sieve, the heat pump runs longer, is sized higher, and its real SCOP deteriorates. After coherent insulation work, needs drop, the heat pump can be smaller, and the environmental gain becomes clearer. The decision therefore follows a logical order: insulate first, then size for the target building envelope.

High-temperature radiators vs underfloor heating: consequences for consumption

With high-temperature radiators, the heat pump has to work harder, and its SCOP drops (typically 2.0 to 2.5 in field measurements from ADEME/OPEN campaigns). The result is more kWh consumed for the same comfort. Underfloor heating, or radiators oversized for low-temperature operation, improve efficiency. On the boiler side, condensation works better with a colder return temperature. Lower temperatures win points on both sides.

Climate, domestic hot water use, controls: the scenarios that flip the verdict

In a cold climate, a heat pump can lose performance, especially at peak demand. A large domestic hot water (DHW) need, a poorly set heating curve, or faulty ventilation can also cancel out the expected advantage. Conversely, good controls, optimised DHW, and a correctly sized generator make the LCA more favourable. Document the real-world scenarios before deciding.

Talking points for tradespeople in 2026: how to explain the LCA to your client

Speak in concrete impacts: kWh, tonnes of CO₂ over time, and orders of magnitude

Explain the LCA as a balance sheet over the whole cycle: manufacturing, transport, installation, use, end of life. Then bring everything back to two reference points: the kWh saved and the tonnes of CO₂ over 15 to 25 years. With sourced orders of magnitude (ADEME Base Empreinte, FDES, PEP), the client quickly understands what really matters.

Supporting documents and traceability: paperwork, product sheets, maintenance, compliance

For a credible LCA, keep simple evidence. Technical data sheets, references, batch numbers, and environmental declarations such as FDES or PEP when they exist. Add the maintenance manual and commissioning report. A well-kept file avoids disputes and protects the job.

2026 subsidies and obligations: linking the LCA to MaPrimeRénov', CEE, and RGE requirements

In 2026, subsidies mainly look at performance and compliance: RGE for MaPrimeRénov', technical criteria and detailed invoices for CEE. The LCA isn't always required, but it helps decide between two eligible solutions. It's your guiding thread for making the right choice.

Sources and references

• Base Empreinte® ADEME — electricity emission factors (average and heating use), natural gas
• F-Gas regulation — leak-tightness and traceability obligations for refrigerants
• IPCC AR6 (2021) — GWP100 / GWP20 factors for fossil methane
• FDES and PEP declarations from heat pump manufacturers (from the INIES database)