How can you improve your home’s energy rating in Luxembourg?
By Yacine Sahnoune, founder of renov.lu
In Luxembourg, a house rated F uses 208 to 295 kWh/m² a year of primary energy; to reach class C it must drop to 123 kWh/m² at most, 40 to 58% less. Insulation mainly improves the thermal insulation class, while a heat pump and solar panels improve the energy performance class, and gaining at least two insulation classes unlocks a Klimabonus bonus of +20% to +50%.
- Nine classes, three indicators: A+ to I for energy performance, thermal insulation and environmental performance (CO₂)
- House thresholds (primary energy): A ≤ 41, B ≤ 90, C ≤ 123, D ≤ 142, E ≤ 208, F ≤ 295 kWh/m² a year
- Klimabonus bonus: +20% on the insulation grant if the insulation class reaches C, +30% for B, +50% for A or A+, with at least two classes gained
- Proof: an energy performance certificate before and one after the works; the bonus can be earned in stages
- Certificate: valid for 10 years, about €500 to €600 for a house, issued for the whole building in co-ownership
- Adverts: the energy class and the thermal insulation class must appear in every sale or rental advert
How many classes can your home gain?
The simulator suggests the works that gain the most classes and calculates the 2026 grants, class bonus included.
The three certificate indicators and the class thresholds
Luxembourg’s energy performance certificate (CPE, or « Energiepass ») gives three independent classes, from A+ to I, under the grand-ducal regulation of 9 June 2021: you can improve one without changing the others.
| Indicator | What it measures | What improves it |
|---|---|---|
| Energy performance | Primary energy used (heating, hot water, ventilation, auxiliaries) | Insulation, heating system, solar production |
| Thermal insulation | The building’s heat demand, which depends on the envelope and air renewal | Roof, walls, floor, windows, airtightness, heat-recovery ventilation |
| Environmental performance | CO₂ emissions from the energy used | Moving away from oil and gas, renewable energy |
Energy performance class thresholds for a detached house
| Class | Primary energy (kWh/m² a year) |
|---|---|
| A+ | ≤ 22 |
| A | ≤ 41 |
| B | ≤ 90 |
| C | ≤ 123 |
| D | ≤ 142 |
| E | ≤ 208 |
| F | ≤ 295 |
| G | ≤ 395 |
| H | ≤ 530 |
| I | > 530 |
Thresholds differ for apartment buildings. The new European A to G scale set by the 2024 directive has not yet been transposed in Luxembourg: the A+ to I scale still applies. What the certificate contains and how to get one: the energy performance certificate.
Which works gain classes
Insulating the envelope mainly improves the thermal insulation class, which no heating change can improve; conversely, a heat pump or solar panels improve energy and environmental performance without touching the insulation class.
| Works | Thermal insulation | Energy performance | Environmental (CO₂) | Reference price |
|---|---|---|---|---|
| Roof and loft | Strong | Strong | Medium to strong (with fossil heating) | €35-350/m² |
| External walls | Strong | Strong | Medium to strong | €150-300/m² |
| Triple-glazed windows | Medium | Medium | Low to medium | €500-2,400 per window |
| Floor, cellar ceiling | Low to medium | Low to medium | Low | €35-60/m² |
| Heat-recovery ventilation | Medium (less loss through air) | Medium | Low | €6,000-18,000 |
| Heat pump replacing oil or gas | None | Strong | Strong | €12,000-24,000 |
| Photovoltaics | None | Medium to strong | Medium | See the solar page |
Qualitative effects derived from what each indicator measures; the real gain depends on the starting point, compactness and orientation, and only a certifier’s or energy advisor’s calculation puts a figure on it. Detailed prices: insulation costs, external wall insulation, heat-recovery ventilation, heat pumps, solar panels.
Example: what it takes to go from F to C
A 150 m² house using 250 kWh/m² of primary energy a year (class F) must fall to 123 kWh/m² to reach C, a 51% reduction, from 37,500 to 18,450 kWh a year. This case is common: according to our survey of houses’ renovation potential, most houses estimated on renov.lu are in class F or G.
A single item rarely achieves such a drop. The combination that most often gets there pairs roof and wall insulation (which cuts heat demand) with a heat pump (which cuts the primary energy needed to meet that demand), with heat-recovery ventilation and windows consolidating the gain. To aim for B (90 kWh/m²) or A (41 kWh/m²), solar production becomes almost essential. The energy advisor simulates each combination before the works: see the energy advisor.
The Klimabonus class bonus: +20% to +50%
The 2026 Klimabonus increases the insulation grant by 20% if the thermal insulation class reaches C, by 30% if it reaches B and by 50% if it reaches A or A+, provided at least two classes are gained, proven by a certificate before and after the works.
- In stages: the bonus can be earned over several rounds of works, for example the roof one year and the façade the next.
- Cap: the bonus stays within the 60% limit of the cost excluding VAT. On an item already capped (loft, rafters) it adds nothing; on a mineral-insulated façade it pays in full.
- Thermal bridge calculation: if class C is reached, the energy advisor receives €160 per calculation, up to €800.
150 m² façade in rock wool, standard II, quote €27,750 excluding VAT, approval in principle requested in 2026: €80 × 150 m² = €12,000 of grant; with the insulation class moved from F to B (+30%), the grant rises to €15,600, below the €16,650 cap. The bonus is worth €3,600. All amounts: grants and the 2026 Klimabonus; effect of the cap item by item: net cost of insulation.
In which order to act to gain classes
To gain classes without redoing works, insulate the envelope first, then provide ventilation, then replace the heating, and finish with solar production: a heat pump sized after insulation is smaller, cheaper and more efficient. The full order, step by step, is in our guide to energy renovation in Luxembourg.
A new certificate after the works: when it is mandatory
A new certificate is mandatory after a change requiring a permit or a substantial transformation affecting energy performance; it is not required for works on less than 10% of the area of elements with the same function, or for a technical installation costing under €1,500 (house) or €3,000 (apartment building).
- For the Klimabonus, the « after » certificate is required anyway with the payment request; it is also what proves the class bonus.
- To sell or let, a valid certificate is mandatory: the one from before the works remains legally valid for 10 years, but shows an outdated class.
- Who and how much: an architect or consulting engineer registered with the OAI, or an approved expert; fees are not regulated, about €500 to €600 for a house. See how to get a certificate and what it costs.
Energy class and property value: renovating before you sell
The energy class weighs on price because it is visible: the energy performance class and the thermal insulation class must appear in every sale or rental advert, and the buyer receives the original certificate.
In a market where an existing flat sells for an average of €7,795/m² (Housing Observatory, second quarter of 2026), each percentage point of value is worth about €78/m². The price gaps observed between classes, with their sources, are analysed on our page on the impact of the certificate on property prices.
- Works that change the class: insulation, windows, ventilation, heating, solar. Start early: allow time for the grant procedure, the works and the new certificate before listing.
- Works that change appeal, not the class: kitchen, bathroom, floor coverings, extension. They add value in other ways: see bathroom renovation costs and kitchen costs.
- Seller’s obligations: handing over the certificate, showing it in the advert, penalties — see obligations when selling.
Improving the rating of a flat
In co-ownership, the certificate is issued for the whole building; a certificate per flat is only possible as a supplement. A flat’s class therefore only really improves with collective works: façade, roof, shared heating.
Since 1 October 2022, energy renovation of common parts is voted by a majority of the votes of all co-owners, and a works fund has been mandatory since 1 August 2023. Inside your own flat, internal wall insulation or new windows improve comfort and bills, but barely change the building’s class. Collective approach: works in co-owned buildings.
Estimate your class gain
The energy renovation simulator suggests the right combination of works for your home and calculates the 2026 grants, class bonus included. For a real project, three companies established in Luxembourg send you a quote.
Frequently asked questions about energy ratings in Luxembourg
What consumption corresponds to class B for a house in Luxembourg?
At most 90 kWh of primary energy per m² a year for the energy performance class of a detached house. Class A stops at 41 kWh/m², class C at 123 kWh/m² and class D at 142 kWh/m². Apartment buildings have different thresholds.
Is a heat pump enough to gain classes?
It improves the energy performance class and the environmental class, because it cuts primary energy and CO₂ compared with oil or gas. It does not change the thermal insulation class, which only depends on the building’s heat demand: yet it is that class which triggers the Klimabonus class bonus.
Can the Klimabonus class bonus be earned in several stages?
Yes. The +20%, +30% or +50% bonus on the insulation grant can be earned in stages, provided you gain at least two thermal insulation classes in total and reach C, B or A, backed by a certificate before and after the works.
Do you need a new energy performance certificate after works?
Yes after a substantial transformation affecting energy performance, unless the works cover less than 10% of the area concerned or a technical installation costing under €1,500 in a house. To receive the Klimabonus, the « after » certificate is required anyway.
Can you improve the rating of a single flat in a building?
Only marginally. In Luxembourg the certificate is issued for the whole building, and a certificate per unit only exists as a supplement. Insulating your walls from inside or replacing your windows improves the flat’s comfort, but the class only rises clearly with works voted by the co-owners.
Renovating before selling: which works should come first?
Those that change the class shown in the advert: roof and wall insulation, then heating and windows. The kitchen and bathroom change the property’s appeal but not its class. Allow several months, as the new certificate must be issued after the works and before the property goes on sale.