The decree of September 12, 2026, sets a threshold of 79 gCO₂e/kWh PCI for any heating equipment installed in new buildings. This threshold effectively excludes gas boilers, including those used as supplementary or hybrid systems, starting January 1, 2027, for new housing. We observe that this regulatory shift redistributes the cards of economical heating well beyond just the new segment.
Carbon threshold at 79 g: what the decree changes for the choice of economical heating
Confusion persists regarding the actual scope of this regulation. In existing buildings, the threshold remains at 300 gCO₂e/kWh PCI. Replacing a gas boiler with another gas boiler in an old home remains perfectly permitted, even after 2027.
However, no national aid is attached to this gas-to-gas replacement. The gap between what is legal and what is funded creates a blind spot for owners renovating on a tight budget. Gas in existing buildings is not prohibited, but it is no longer supported.
New public buildings will follow in 2028, and then other new buildings in 2030. To keep track of the evolution of these timelines and their repercussions on eligible equipment, the Chauffage Économique news allows for cross-referencing regulatory updates with feedback from installers.
This gap between new and existing has a direct consequence on the market: manufacturers of condensing gas boilers maintain their ranges for renovations, while all innovation focuses on low-carbon systems for new builds.
Heat pump and photovoltaic coupling: actual profitability of the combo
The coupling of heat pumps and photovoltaic panels goes beyond marketing promises. In direct self-consumption, the heat pump absorbs a significant portion of daytime solar production, reducing dependence on the grid during peak hours.
We recommend sizing the photovoltaic field based on the consumption profile of the heat pump, not the available roof area. Oversizing solar without battery storage generates a surplus sold at an unattractive rate, extending the return on investment without real thermal benefit.
Points of caution on sizing
- The air-water heat pump coupled with solar works best when the buffer tank is large enough to store the heat produced during the day and release it in the evening.
- The actual COP of the heat pump drops in extreme cold, precisely when photovoltaic production is at its lowest, which necessitates checking the compatibility of the system with the local climate.
- The hybrid inverter (solar + grid) must manage the power supply priority of the heat pump without causing micro-cuts, a setting that many installers overlook.
Poor solar sizing degrades profitability instead of improving it. It is better to have three well-utilized kilowatts-peak than an oversized installation where the surplus sits idle on the grid.
Connected thermostat and room-by-room control: beyond the gadget
The connected thermostat is no longer limited to programming time slots. Recent models incorporate window opening detection, learning of heating-up times, and weather forecasting to adjust the heating curve.
The technical challenge lies in room-by-room control via connected thermostatic heads. A south-facing living room does not have the same needs as a north-facing bedroom. Without zoning, the central thermostat imposes a compromise that overheats some rooms and underheats others.
Communication protocols and interoperability
The choice of radio protocol (Zigbee, Z-Wave, Thread) determines the reliability of the system. A Thread mesh network offers better range and lower latency than a standard Zigbee in homes with thick walls. We observe that interoperability between brands remains the main barrier to truly unified control.
A Netatmo thermostat will struggle to control Tado heads without going through a third-party hub. The Matter protocol, intended to unify the ecosystem, is progressing slowly in the heating sector. Before investing, checking compatibility between the thermostat, valves, and boiler or heat pump avoids unnecessary expenses on gateways and adapters.
Low-temperature emitters: the often-overlooked link
Installing a high-performance heat pump on a high-temperature radiator network effectively throttles the system. The efficiency of a heat pump directly depends on the water supply temperature. Reducing the output temperature from 65 °C to 40 °C from the heat pump significantly improves the seasonal COP.
Low-temperature underfloor heating remains the most coherent solution in new builds. In renovations, low-temperature radiators with high inertia (large surface area steel exchangers) allow for lowering the supply temperature without floor work.
Existing radiators: keep or replace
An old cast iron radiator, often oversized for current needs (additional insulation since), can operate at low temperature if its exchange surface is sufficient. Before replacing everything, a room-by-room heat loss calculation determines if the existing emitters can support a water regime at 45 °C.
Replacing only undersized radiators costs significantly less than a complete change. This emitter diagnosis, rarely offered by installers, is crucial for the overall profitability of switching to a heat pump.
Economical heating in 2026 is not just about choosing a generator. Carbon regulation, solar coupling, connected control, and emitter sizing form a system where each link influences the final bill. Neglecting any of these elements is enough to turn a profitable investment into an under-optimized expense.
