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Klimabonus 551

Air-to-water heat pump

What is Klimabonus 551?

Klimabonus 551 is a public subsidy scheme in Luxembourg supporting the installation of air-to-water heat pumps in residential buildings.

An air-to-water heat pump uses energy from the ambient air to provide heating for the building. It is a renewable heating solution that helps reduce fossil fuel consumption and supports climate protection.

Technical requirements for air-to-water heat pumps

To be eligible for Klimabonus 551, the installation must meet the following technical requirements:

General technical requirements

  • Hydraulic balancing must be carried out after installation.

  • Installation of:

    • a separate or integrated electricity meter for the heat pump,

    • a separate or integrated heat meter for the heat pump.

Additional requirements for existing buildings

  • Installation of a buffer tank (boiler) with a minimum capacity of
    30 litres per kWth of heating power.

  • This requirement does not apply to heat pumps equipped with a frequency converter (inverter) allowing speed or power modulation.

Performance requirements

  • The heat pump must meet the following coefficient of performance (COP) requirements in accordance with EN 14511:

    • Air-to-water heat pump (including exhaust air heat pumps):
      COP ≥ 3.1 at A7/W35

Noise level requirements

    • The sound power level (Lw) of the external unit must comply with the following limits (according to the ErP label):

      • ≤ 5 kW: max. 48 dB(A)

      • > 5 kW and ≤ 12 kW: max. 51 dB(A)

      • > 12 kW: max. 55 dB(A)

      If the external unit exceeds these limits, the measured value may be reduced by installing additional soundproofing or noise protection equipment.

      Alternatively, if the sound power limits are not met:

      • the noise level at the boundary of the nearest building land must not exceed 40 dB(A),

      • compliance must be proven by an acoustic assessment based on a calculation tool provided by the Ministry,

      • this assessment must be carried out before installation.

Requirements for new buildings

For new buildings:

  • the heating system must be designed to supply the heating circuit with a maximum flow temperature of 35°C (W35).

  • If this is not possible, the heat pump must still achieve COP ≥ 3.1 at the selected operating temperature.

Hybrid systems

For non-fossil hybrid systems:

  • at least 70% of the annual heat demand must be covered by the heat pump.

Conditions for receiving the subsidy

  • To receive Klimabonus 551, the following conditions apply:

    • The subsidy is available only for heating systems in residential buildings.

    • Only one heating system can be subsidised per residential building:

      • heat pump, or

      • wood heating system, or

      • connection to district heating.

    • No state subsidy must have been requested for a technical installation under the 2016 or 2022 subsidy programmes.

    • In the case of a hybrid system, the heat pump must cover at least 70% of the annual heat demand.

How to apply for Klimabonus 551

  • The subsidy application can be submitted after the installation has been completed.

Social Top-Up Klimabonus

Eligible households may apply for a social top-up subsidy after receiving the decision granting the Klimabonus subsidy.

Applications must be submitted to:

Single Point of Contact for Housing Assistance
11, rue de Hollerich
L-1741 Luxembourg
Grand Duchy of Luxembourg
📧 guichet@ml.etat.lu
📞 (+352) 8002 10 10

Required application forms

Klimabonus – basic subsidy

  • “Demande d’une aide dans le cadre du paquet banque climatique et logement durable – DEPA-2026 – Personne physique”
    (or the form for Personnes morales)

  • “Chaudière à bois – Fiche BOIS 2026”

  • Or submission online via www.myguichet.lu
    (only for private individuals and single-family homes)

Social Top-Up Klimabonus

  • “Demande en obtention d’une aide à l’assainissement énergétique (F3)”

  • “Déclaration relative à la composition de la communauté domestique (L/A21)”

  • “Déclaration sur l’honneur – Acquisition (A92)”

Validity of the Klimabonus 551 scheme

The Klimabonus 551 basic subsidy applies to:

  • invoices dated between 1 January 2026 and 31 December 2030,

  • subject to the finalisation of the legislative process for draft bill No. 8585.

The subsidy rules described on this page are based on the official framework defined by Klima Agence.
As regulations may evolve, Klima Agence remains the final authority for validation.
We stay aligned with their latest guidelines to ensure our clients receive accurate and reliable information throughout the process.

Our experts help you assess whether an air-to-water heat pump is suitable for your home, explain the technical requirements in clear terms, and guide you through the Klimabonus 551 subsidy conditions. Get practical advice, clear answers and support with the next steps free of charge and without obligation.

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FAQ – Frequently Asked Questions

What does Klimabonus 551 support?

Klimabonus 551 supports the installation of air-to-water heat pumps in residential buildings, using renewable energy from the ambient air to provide heating.

Who can apply for Klimabonus 551?

The subsidy is available only for residential buildings, provided all technical and administrative requirements are met.

What technical requirements must the heat pump meet?

The installation must include: hydraulic balancing after installation, a separate or integrated electricity meter, a separate or integrated heat meter. Additional requirements may apply depending on the building type.

Is a buffer tank required?

Yes, for existing buildings, a buffer tank of at least 30 litres per kWth of heating power is required. This does not apply to inverter heat pumps with speed or power modulation.

What performance level is required?

The heat pump must achieve a Coefficient of Performance (COP) of at least 3.1 at A7/W35, in accordance with the EN 14511 standard.

Are there noise level requirements?

Yes. The outdoor unit must comply with defined sound power limits depending on system size. If these limits are exceeded, additional soundproofing may be used, or an acoustic assessment must demonstrate that noise levels at the nearest property boundary do not exceed 40 dB(A).

Are different rules applied for new buildings?

Yes. For new buildings, the heating system must be designed to operate with a maximum flow temperature of 35°C (W35). If this is not possible, the heat pump must still achieve the required COP value at the chosen operating temperature.

Are hybrid heating systems eligible?

Yes, provided the system is non-fossil and the heat pump covers at least 70% of the annual heat demand.

Can I receive multiple heating subsidies for one building?

No. Only one heating system can be subsidised per residential building: heat pump, or wood heating system, or connection to district heating.

When can I apply for the subsidy?

The subsidy application can be submitted after the heat pump installation has been completed.

Is a social top-up subsidy available?

Yes. Eligible households may apply for a Social Top-Up Klimabonus after receiving the decision granting the basic subsidy.

Who makes the final decision on the subsidy?

Final eligibility and approval are determined by the competent public authority, in accordance with the applicable legislation.

How long is Klimabonus 551 valid?

The Klimabonus 551 basic subsidy applies to invoices dated between 1 January 2026 and 31 December 2030, subject to the final adoption of draft bill No. 8585.