How to improve your energy class in Luxembourg: works, grants and property value
In Luxembourg, moving from energy class E or F to class B or C is not only achievable but financially very advantageous: the Klimabonus Wunnen 2026 refunds up to €12,000 for a geothermal heat pump, insulation works benefit from flat-rate grants in €/m², and Immotop.lu data confirms that a class A-C property sells for up to €1,400 to €2,600/m² more than a class F-G property in the Centre region. This page explains which works have the strongest impact on your energy passport, in what order to carry them out, and how to maximise the subsidies available — while avoiding costly mistakes.
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The three EPC classes: what you can improve
Before committing to works, it is essential to understand that the Luxembourg energy passport assigns three independent classes, each calculated using different criteria by the LuxEeB-Tool or Lesosai software (approved by the Ministry of the Economy). Improving just one may be enough for your objective; improving all three simultaneously constitutes a global renovation that maximises Klimabonus grants.
| EPC class | What it measures | What improves it most |
|---|---|---|
| 1. Energy performance class Primary energy — A+ to I |
Total primary energy requirement of the building: heating, DHW, ventilation, lighting | Heating type (heat pump, wood boiler), photovoltaic production, solar thermal |
| 2. Thermal insulation class Heating demand — A+ to I |
Building envelope quality: losses through walls, roof, floor, windows and air renewal | Roof insulation, external walls, floor, window replacement, air tightness, double-flow ventilation |
| 3. Environmental performance class CO₂ emissions — A+ to I |
CO₂ emissions from energy consumed for building operation | Replacing fossil heating with heat pump or renewables, photovoltaic |
💡 Useful tip
Your energy passport already contains, on pages 3 to 5, personalised modernisation recommendations with projected savings per work item. This is your first roadmap: re-read your current EPC before contacting tradespeople. If you do not yet have an EPC or it has expired, an approved expert can produce a pre-works simulation.
Important reminder confirmed by Klima-Agence and guichet.public.lu: the energy passport and its results create no legal renovation obligation, whatever class is achieved. However, your class directly determines your property’s market value and the scale of grants available to renovate it.
Property value: what the energy class actually changes in Luxembourg
The energy class has become a major property valuation criterion in the Grand Duchy, confirmed by Immotop.lu and STATEC data. For more on the relationship between EPC and property value, see our dedicated page on the impact of the EPC on property prices.
Price gaps by region (Immotop.lu data, Q1 2025)
According to quarterly analyses by Immotop.lu (Q1 2025), a class A-C property sells for an average of up to €1,400/m² more than a class F-G property nationally — with markedly higher gaps by region:
| Region | Price gap A-C vs F-G (€/m²) | Example: 120 m² house |
|---|---|---|
| Centre region (Luxembourg City and nearby) | +€1,563 to €2,611/m² | +€187,560 to +€313,320 |
| South region (Esch-sur-Alzette and surroundings) | +€1,347 to €1,700/m² | +€161,640 to +€204,000 |
| East region | +€1,148 to €1,224/m² | +€137,760 to +€146,880 |
| West region | +€671 to €1,207/m² | +€80,520 to +€144,840 |
| North region | +€172 to €434/m² | +€20,640 to +€52,080 |
STATEC has further documented in joint studies with the Housing Observatory that a class A-B-C house sells for an average of 9.9% more than a class D-E-F house, and up to 38.3% more compared to low energy efficiency properties.
Energy bill savings
Beyond property value, a well-executed renovation generates direct savings on running costs. A typical pre-1990 Luxembourg house consumes around 150–200 kWh/m²/year (class E-F). After full envelope insulation and heating replacement with a heat pump, this can fall to 60–80 kWh/m²/year (class B-C), representing a 40 to 60% reduction in heating costs. For a 150 m² house, this amounts to €1,500–2,500 in annual savings depending on the energy replaced.
Works ranked by impact on energy class
Not all renovation works carry the same weight in the LuxEeB calculation. Here is the ranking by actual impact on the three EPC classes, established against the calculation method of the Grand-Ducal Regulation of 9 June 2021 and Klima-Agence technical data. Our page on where to start your energy renovation also covers these priorities in a practical context.
The most powerful lever on the energy performance class and environmental performance class. An air-water heat pump with COP ≥ 3.1 for A2/W35 (Klimabonus 2026 technical condition) divides the primary energy index by 2 to 3 compared to a gas or oil boiler. Typical gain: 1 to 2 energy performance classes. Cost before grants: €12,000–18,000. Klimabonus 2026: up to €10,000. See our guides on oil boiler replacement and gas boiler replacement.
Even more efficient (COP ≥ 4.3 for B0/W35 required). Constant efficiency regardless of outdoor temperature. Typical gain: 2 energy performance classes. Cost before grants: €20,000–30,000. Klimabonus 2026: up to €12,000.
The roof accounts for 25 to 30% of heat loss in a poorly insulated house. Recommended minimum thickness: 25 to 30 cm. Typical EPC gain: 0.5 to 1 thermal insulation class. Cost: €40–80/m². See our guide on roof and loft insulation.
Walls account for 20 to 25% of heat loss. External insulation eliminates structural thermal bridges and preserves habitable floor area. Typical gain: 0.5 to 1 thermal insulation class. Cost: €80–200/m². Klimabonus 2026: €60/m² (standard) to €115/m² (eco-material, more than 50% recycled content).
Klimabonus 2026 condition: Uw ≤ 1.4 W/m²K. Flat-rate grant: €70/m² of glazed area replaced. Typical gain: 0.3 to 0.5 thermal insulation class.
PV production is directly deducted from primary energy needs in LuxEeB. Klimabonus 2026: up to €10,000 for installations up to 15 kWp, with direct pre-financing from January 2026. See: solar panel grants in Luxembourg.
Reduces ventilation heat losses by 60 to 90% compared to natural ventilation. Improves both thermal insulation class and energy performance class. Essential in any building with reinforced air tightness. Only systems with heat recovery have been eligible for Klimabonus since 2022.
⚠️ Important
These class gain estimates are indicative. The actual impact depends on the building’s initial state, compactness, energy reference area (ERA) and the specific performance of installed materials and equipment. Only an approved expert using LuxEeB-Tool or Lesosai software (officially recognised by the Ministry of the Economy) can simulate the precise class gain for your building.
In what order should works be carried out?
The order of works is as important as the works themselves. Klima-Agence and approved energy advisers recommend the following sequence. Our guide on energy renovation steps in Luxembourg also covers this logic in detail.
Before any investment, an on-site energy advisory from a certified Klima-Agence adviser diagnoses your building’s thermal state precisely (thermal bridges, air leaks, envelope condition), simulates class gains for each work combination, and establishes a sequenced renovation plan forming the basis for multi-element Klimabonus applications. Note: the EPC and the energy advisory are two distinct documents. The energy passport rates your building; the energy advisory plans how to improve it and in what order. Klima-Agence offers a free first consultation (T. 8002 11 90 or klima-agence.lu).
Roof, external wall, floor insulation and window replacement must precede heating system replacement. A heat pump installed in a poorly insulated building will need to deliver much more energy to offset thermal losses, degrading its real performance (effective COP below nominal COP), increasing running costs and reducing durability. A better-insulated building can be heated by a lower-powered heat pump. It is also at this stage that thermal bridges should be addressed.
A better-insulated building is also more airtight. Without sufficient air renewal, indoor air quality deteriorates rapidly: excess humidity leading to mould, CO₂ concentrations exceeding health thresholds, accumulation of pollutants. Installing MVHR ventilation after insulation work ensures healthy air while recovering heat from extracted air. An airtightness (blower door) test can validate results.
Only after reducing demand and securing ventilation can the heat pump be optimally sized. Its impact on the energy performance class is then maximised as the residual demand it must cover is minimal. See: heat pump sizing and power.
Photovoltaic, solar thermal or connection to a renewable heat network allows the best EPC classes (A or A+) to be reached, approaching the NZEB (Nearly Zero Energy Building) standard, mandatory for new builds in Luxembourg since 2017.
Klimabonus Wunnen 2026: available grants to improve your EPC class
The Klimabonus Wunnen 2026 scheme came into force on 1 January 2026 (retroactive effect, subject to final publication in the Luxembourg Mémorial — bill 8585 was filed in July 2025). It succeeds the 2022 scheme with major simplifications and improvements. For full details, see our pages on Klimabonus grants for energy renovation and Klimabonus loan financing.
📋 Key Klimabonus 2026 conditions
The building must be more than 10 years old (building permit date). The preliminary approval request must be submitted between 1 January 2026 and 31 December 2030. Invoices must be issued between 1 January 2026 and 31 December 2035. Works must be carried out by an approved company or supervised by an approved energy adviser.
| Installation | Klimabonus 2026 grant | Key technical condition |
|---|---|---|
| Air-water heat pump (fossil boiler replacement) | up to €10,000 | COP ≥ 3.1 for A2/W35; buffer tank ≥ 30 l/kWth (existing building) |
| Geothermal ground-water heat pump (fossil boiler replacement) | up to €12,000 | COP ≥ 4.3 for B0/W35 |
| Photovoltaic installation (with direct pre-financing) | up to €10,000 | Min. 2 kWp; ceiling reached at 15 kWp |
| Storage battery (paired with PV) | up to €2,250 | Ceiling reached at 9 kWh capacity |
| External wall insulation (standard, performance level I) | €60/m² (standard) / €115/m² (eco-material) | Eco rate: certified material containing more than 50% recycled content |
| Window replacement (Uw ≤ 1.4 W/m²K) | €70/m² of glazed area replaced | Uw ≤ 1.4 W/m²K mandatory |
⚠️ Absolute rule — preliminary approval required
Never start works before obtaining preliminary approval from the Environment Administration (via MyGuichet.lu or a certified tradesperson). Works started without approval lead to automatic and final rejection of the Klimabonus application, with no appeal possible. This rule is non-negotiable and applies to each work item individually.
When and why get a new EPC after works?
Your current EPC remains legally valid until expiry (10 years), but it no longer reflects your actual class if works have improved your building. This creates a gap between the real value of your property and its displayed value in listings or sale documents — a direct financial loss, especially in the Centre and South regions. For details on costs and procedures, see our page on energy passport costs in Luxembourg.
Cases where a new EPC is mandatory after works
- Works on the thermal envelope covering more than 10% of an element’s area (external wall, roof, window…) — regulatory obligation under the Grand-Ducal Regulation of 9 June 2021
- Works on technical installations (heating, ventilation…) exceeding €1,500 for a single-family home or €3,000 for a multi-family home
Cases where a new EPC is strongly recommended
- Resale after renovation: an updated EPC reflects your improved class and can justify a significant premium in listings and negotiation. See: energy passport obligations when selling.
- Letting after major works: the new class improves the property’s attractiveness and anticipates potential rental regulation on energy-inefficient properties.
- Financing applications (climate loan, green mortgage): some Luxembourg financial institutions take the post-works EPC class into account for loan conditions.
Works completed and want a new EPC reflecting your improved class? Our approved experts issue your new energy passport and guide you through the process.
Special case: improving the EPC class of a co-ownership apartment
An apartment’s situation is fundamentally different from a single-family house. In Luxembourg, the energy passport is established for the entire building, not the individual unit. The EPC class on your certificate is therefore that of the building as a whole, calculated on the basis of its global envelope, collective heating system and common installations. As an apartment owner, you cannot improve your EPC class unilaterally.
What can be done individually
At your apartment’s level, possibilities are limited to replacing a separate individual heating system (uncommon in Luxembourg co-ownerships where collective heating is the norm) and small improvements such as replacing your windows if co-ownership rules permit. These actions have very limited impact on the LuxEeB calculation, which covers the entire building.
What requires collective action
To genuinely improve the building’s EPC class, collective action is required through the syndic or co-owners’ assembly on: roof and loft insulation, facade insulation (EWI or cladding), collective heating system replacement with a heat pump, collective double-flow ventilation, and rooftop photovoltaic installation. Klimabonus Wunnen 2026 grants are fully accessible to co-owners’ associations. Klima-Agence provides free consultations for co-ownerships (T. 8002 11 90).
Strategies depending on your objective
Depending on your situation and time horizon, the optimal improvement strategy differs. Here are the four most common approaches in Luxembourg.
In the Centre and South regions, roof insulation combined with heat pump replacement typically generates a property premium well above the residual cost after Klimabonus. Always obtain the Klimabonus preliminary approval before any order. Have the new EPC issued immediately after works to reflect your investment in listings. See our page on the EPC impact on property prices for detailed regional figures.
Opt for sequenced global renovation following the 5 steps above. With Klimabonus 2026, 3% VAT, Enoprimes and cumulative bill savings, more than 50% of the total investment can be covered. Return on investment is typically reached in 4 to 8 years. See our page on Klimabonus loan financing to spread the financial effort over time.
The fastest and most impactful lever is replacing the fossil boiler with an air-water heat pump. Typical timeline: preliminary approval → installation → new EPC in 4 to 10 weeks. Never order or sign a binding quote before preliminary approval via MyGuichet.lu.
Achievable for an existing building through complete renovation: high-performance insulation of all elements, double-flow ventilation, high-efficiency heat pump, PV self-consumption and solar thermal. Estimated budget: €50,000 to €100,000, covered 40–60% by cumulative Klimabonus grants. Always consult an approved energy adviser to simulate the precise feasibility for your specific building.
Your renovation project, supported from A to Z
Energy audit, work selection, Klimabonus application, referral to approved tradespeople and new EPC after works: Renov.lu supports you at every step to maximise your class gain and grants.
Frequently asked questions about improving energy class in Luxembourg
How many classes can be gained with a complete renovation in Luxembourg?
A global renovation combining full envelope insulation (roof, walls, floor, windows), double-flow ventilation and replacement of fossil heating with a heat pump typically achieves 3 to 5 class gains on the energy performance class. A class F house can reach class B or even A. Only an approved expert using LuxEeB-Tool or Lesosai software can simulate the precise gain for your property.
Am I legally obliged to renovate if my EPC shows a poor class?
No. In Luxembourg, no legal renovation obligation arises from energy passport results, whatever class is achieved — from A+ to I. This is expressly confirmed by Klima-Agence and guichet.public.lu. However, your EPC class directly affects your property’s market value, its attractiveness to buyers and tenants, and the scale of Klimabonus grants available to improve it.
What is the maximum amount of grants that can be combined for a complete renovation?
By combining all Klimabonus Wunnen 2026 grants for a global renovation, a single-family home can theoretically benefit from over €35,000 in Klimabonus grants alone, plus Enoprimes, municipal grants, 3% VAT on all works, and the social top-up doubling grants for eligible low-income households. Use the official simulator at aides.klima-agence.lu for exact amounts.
Does photovoltaic installation really improve the EPC class?
Yes, directly. In the LuxEeB calculation for residential buildings, PV production is deducted from the building’s primary energy index, improving the energy performance class (1st EPC class) and to a lesser extent the environmental performance class (CO₂). The effect is further amplified when the heat pump uses self-produced electricity.
Is preliminary Klimabonus approval truly mandatory before starting works?
Yes, this is an absolute, non-negotiable condition of Klimabonus Wunnen 2026. Preliminary approval must be obtained from the Environment Administration — via MyGuichet.lu or via a certified tradesperson — before any works begin and before signing any binding quote. Works started without approval lead to automatic and final rejection of the grant application, with no exception possible.
My home is a co-ownership apartment — can I still benefit from Klimabonus?
Yes, but collectively. Klimabonus Wunnen 2026 grants are accessible to co-owners’ associations for works on common areas (roof, facades, collective heating system, collective ventilation, rooftop PV). Klima-Agence provides free support to co-ownerships in this process (T. 8002 11 90).