Why should one not start by choosing a technology?
When a boiler ages, the first reaction is often to ask for a price for a new machine. This method sometimes reproduces an oversized or ill-suited piece of equipment.
One must first understand how much heat the building consumes, at what temperatures the network operates and how the hot water is produced. The state of the insulation, the ventilation, the occupancy hours and the settings influence the choice.
The right project is not necessarily the one that replaces the boiler with an equivalent power. A renovation of the envelope or better balancing may reduce the power required.
Can a heat pump work with the existing radiators?
The presence of radiators does not automatically rule out a heat pump. The important question is the water temperature required during cold periods.
A heat pump operates more efficiently with a moderate temperature. If the radiators need very hot water to compensate for the losses, the installation may become less efficient.
The study must measure or estimate the temperatures required. It may propose insulation, the replacement of a few emitters, a hydraulic balancing or an adaptation of the network.
Should one insulate before replacing the boiler?
A full renovation is not always essential before the replacement. On the other hand, ignoring the works planned on the envelope may lead to sizing the equipment for needs that will decrease.
One must at least examine the roof, the façades, the windows and the main losses. The co-ownership may then decide on an overall project or one in stages.
Which solutions to compare?
The collective heat pump uses the energy of the air, the ground or another source. It requires a study of the network, the electrical power, the location and the noise.
The pellet boiler requires sufficient storage, access for deliveries, a suitable flue-gas exhaust and an organisation for maintenance.
Connection to a district heating network may avoid new production in the building, if one exists nearby. One must check availability, timetable, connection, tariff and the origin of the heat.
A hybrid or transitional solution may be contemplated in certain buildings, but its objective must be clear.
A final point conditions the budget: the subsidies come with technical requirements that must appear in the quotes. Depending on the case, this may be a dedicated electricity meter, a heat meter, the hydraulic balancing of the network, a buffer tank sized in litres per thermal kilowatt, minimum coefficients of performance and acoustic power limits for the outdoor unit. An offer that does not include them may cause the subsidy to be lost afterwards.
What becomes of the oil tank?
The project incorporates the emptying, degassing, neutralisation or removal of the tank. Access and reinstatement may represent a significant cost.
The item "removal, neutralisation and recycling of the fuel-oil tank" appears in several Klimabonus scales when the oil-fired boiler is replaced by an installation that is itself eligible, in particular a heat pump, a wood boiler or a connection to a district heating network. It is therefore not a stand-alone subsidy.
A separate line must appear in the quotes and an invoice from a specialised company must be kept.
The tank is also a regulated item. A deposit of diesel oil or other liquid fuels constitutes a classified establishment from 300 litres, a threshold that any collective tank exceeds. Underground tanks taken out of service must be completely emptied, cleaned and neutralised, or removed from the subsoil after degassing; those that are removed must be destroyed in order to make their reuse impossible. These obligations are without prejudice to the application of the legislation on the decontamination and remediation of the subsoil. The cessation of the deposit's activity must be declared to the Environment Administration at the latest within the month that follows.
Which constraints to anticipate?
A heat pump may require additional electrical power. The outdoor unit must be studied for noise, vibrations, air discharge and maintenance.
Pellets require volume and logistics. A district heating network depends on an external operator and timetable.
The project also provides for the continuity of heating, the adaptations of the technical room and the hot water.
Which majority must be reached?
The replacement of a collective boiler by equipment that improves or transforms the existing installation falls to a majority of the votes of all the co-owners. Works classified as energy renovation fall to the same majority. If it is not reached, a new general meeting may decide by a majority of the co-owners present or represented.
Replacement strictly like-for-like, with no improvement or transformation, falls within the maintenance and preservation of the building and is voted under the ordinary-law conditions. This case is now marginal: replacing an oil-fired boiler with a heat pump, a wood boiler or a connection to a district heating network always involves a transformation.
In which order to prepare the decision?
The useful sequence is: diagnosis, network study, comparison of scenarios, estimation of subsidies, uniform quotes, financing and then decision. The plan must incorporate the works fund and check, where collective heating is maintained, the sub-metering obligations and the deadline of 1 January 2027.
The subsidy scheme must be checked just before the order. As of 6 August 2026, Klimabonus 2026 is still presented subject to the final publication of the texts.
Since 19 September 2025, fixed heat pumps connected to a water-based heating circuit are subject to a mandatory acceptance by the Chambre des Métiers, whatever their power. The installer submits the request within the month following commissioning; the acceptance takes place within three months from the notification of the request and gives rise to a protocol to be kept.
Reference texts
- Law of 16 May 1975 establishing the statute of co-ownership of built property (Mémorial A No 28 of 23 May 1975), in particular Articles 11bis, 15 and 16 — Article 11bis (works fund) having been inserted and points e), f) and g) of Article 16 (energy renovation, production and storage of energy) added by the Law of 30 June 2022 (Mémorial A No 347 of 11 July 2022), point d) of Article 16 (transformation of existing equipment) resulting from the Law of 22 April 1985 (Mémorial A No 22 of 9 May 1985)
- Grand-Ducal Regulation of 26 July 1999 on fuel-oil deposits of 300 to 20,000 litres
- Guichet.lu, Klimabonus 2026
- Klima-Agence, "Heat pumps in co-ownership"
- Klima-Agence, acceptance
- Grand-Ducal Regulation of 13 August 2025 on the arrangements for the acceptance of heat pumps
- Law of 10 June 1999 on classified establishments