Energy audit in Luxembourg: What's New in 2026

What actually changed on 1 January 2026, and what did not

The name did not change. Klimabonus has been the name of the Luxembourg housing energy aid scheme since 1 January 2022, the date on which it replaced PRIMe House. What takes effect on 1 January 2026 is a revised set of flat-rate amounts and conditions inside that same Klimabonus scheme. Anyone telling you that Klimabonus replaces PRIMe House « from 2026 » is four years late.

PRIMe House is the closed 2017 scheme. It still concerns you in one situation only: your energy consultancy was established before 31 December 2021 and your invoices are dated between 2017 and 2024. Those files remain admissible until 31 December 2026, and not beyond. Everything you start in 2026 falls under the Klimabonus 2026 rules set out below.

One caveat taken straight from the source: Guichet.lu states that applications can be submitted from 1 January 2026 with retroactive effect, but that their processing remains subject to publication of the law in the Official Journal. Check the amounts on the official page before you sign a quote.

The energy consultation is now the pivot of the whole file

There are three situations, not two, and the one that applies to you decides who has to be involved:

• More than one element of the thermal envelope renovated: the energy consultation (conseil en énergie) is mandatory. It is not an alternative you can trade against something else.
• A single element (pitched or flat roof, an external wall, a ceiling or floor slab in contact with an unheated zone, a wall in contact with an unheated zone or the ground, windows and French windows): the works must be carried out by an approved business, or performed in the presence of an energy consultant.
• Technical installations (heating, ventilation, renewables): no alternative at all, a trade professional is required.

Aid for the energy consultation itself is €1,700 for a single-family house and €2,000 for a building with 2 flats, plus €60 per additional flat, capped at €3,000. Where the increased amounts apply, the same items are €2,000 for a house and €2,500 to €3,750 in a multi-dwelling building. The aid is granted only if at least one energy efficiency measure is actually implemented, and it can never exceed the real cost of the assessment. The consultation invoice must be issued between 1 January 2026 and 31 December 2030 inclusive.

In the single-element route, an energy consultant who occasionally monitors the works can bring €400, plus a €100 supplement for verifying the conformity of the estimates.

Insulation aid is a rate per m2, not a percentage

This is the single biggest correction to make to almost anything written about Luxembourg aid before 2026. The up to 50% of costs, capped at €15,000 figure belongs to PRIMe House, the closed scheme. The 2026 Klimabonus pays a flat rate per m2 of renovated surface, according to the insulation standard reached (III, II or I). The amount in brackets is the increased amount.

Two adjustments decide the final figure. The amount is reduced by 25% if the insulation is fitted exclusively from the inside, and a materials supplement of €15 per m2 can be added. Windows and French windows are subsidised at standard III only.

The procedure, which is where files are actually lost

• For energy renovation of the thermal envelope, an agreement in principle is mandatory before the works start. Sign the quote and let the builder begin first, and the aid is gone.
• The first application for an agreement in principle must be filed between 1 January 2026 and 31 December 2030 inclusive.
• Eligible invoices run from 1 January 2026 to 31 December 2035.
• The aid must be claimed within 4 years counted from 31 December of the year in which the invoice was issued, and at the latest by 31 December 2039.
• Exception: photovoltaic panels and batteries are applied for after the works, with no prior agreement in principle.
• The building must be more than 10 years old, counted from the date the building permit was issued.
• The age of the boiler you are replacing is no longer a criterion since 2026.

Applications are filed with the Guichet unique des aides au logement, and the aid is granted by the Administration de l'environnement (AEV). No processing time is published by the Guichet unique. Do not plan your cash flow around a promised number of weeks, whoever quotes it to you.

Topup Klimabonus: the aid most owners never claim

The Topup Klimabonus is a separate aid from the Ministry of Housing, formally the prime d'amélioration pour assainissement énergétique. It is not part of the Klimabonus and it is not granted automatically.

• It pays 10% to 100% of the Klimabonus amount already granted, depending on the composition and income of your household. In the best case it doubles your aid.
• You must already have obtained a Klimabonus from the Administration de l'environnement, and file the Topup application within 2 years of that grant decision. Miss the window and the right lapses.
• It cannot be combined with the classic prime d'amélioration.
• All capital housing aid combined is capped at €35,000 per beneficiary.
• Income ceilings apply, and the dwelling must serve as your main and permanent home for at least 2 years from the date the aid is granted.

If you are budgeting a renovation, work out the Topup before you decide how much of the project you can afford. It changes the arithmetic more than any negotiation with a contractor will.

VAT at 3%: the condition almost every article gets wrong

The super-reduced rate of 3% applies to housing assigned to main residence use; the standard Luxembourg VAT rate has been 17% since 1 January 2024. There are two routes to it:

• substantial works on a dwelling whose construction is at least 10 years old at the start of the works, the works being carried out within 2 years from their commencement; or
• works completed within 5 years of an acquisition.

You will still find « dwellings more than 2 years old » and « more than 20 years old » in circulation, including in material that has never been updated. Both are wrong. The 2 years is the period during which the dwelling must be assigned to main residence use after the works; the 20 years figure is obsolete.

Two procedures, two thresholds:

• Direct application of the 3% rate: the quote must be at least €3,000 excluding VAT and the request must be filed before the works start.
• Reimbursement afterwards: each invoice must be at least €1,250 excluding VAT, and the request must cover a minimum period of six months.

In both cases the tax advantage is capped at €50,000 per dwelling.

Claims about 2026 that no official source supports

Several figures circulate about the 2026 reform that neither Guichet.lu, the Administration de l'environnement nor Klima-Agence publishes: a digital energy audit made compulsory for every property over 10 years old, a headcount of certified auditors, an average processing time on Guichet.lu, a fixed percentage of energy savings after works, and a five-year validity for an audit. This article previously carried some of them. They have been removed rather than rounded down.

What is official on validity: the certificat de performance énergétique (CPE), the Luxembourg energy passport, is valid for 10 years.

Get your quotes before the agreement in principle

The order matters: quotes first, agreement in principle next, works last. Receive up to 5 free and non-binding quotes from professionals working in Luxembourg, then file your Klimabonus application with figures that hold up.