How to choose the right solar installer in Luxembourg

In Luxembourg, every tradesperson must hold a business licence (autorisation d'établissement) issued by the Ministry of the Economy and be registered with the Chambre des Métiers. It is the prerequisite for Klimabonus eligibility and the key mark of legitimacy: an installation carried out by an unlicensed company can cost you the subsidy.

Always ask for the licence number, the Luxembourg VAT number and the registered office, then cross-check them against the official register. A company based abroad may work in Luxembourg, but it needs a service-provision authorisation, get written confirmation before work starts.

Never rely on a single quote. Vert.lu lets you receive up to three quotes from installers in your area, usually within 48 hours. For the comparison to mean anything, the scope must match: peak power in kWp, panel brand and model, inverter type (string or micro-inverters), mounting system, cabling, commissioning and paperwork.

A 20% price gap almost always has a technical explanation: higher-efficiency modules, a hybrid inverter ready for a battery, per-panel optimisers, or simply scaffolding included or not. Ask each installer to break down the "additional works" line, that is where most end-of-project surcharges hide.

A good installer starts from your annual consumption in kWh, your usage profile and the roof orientation, not from a catalogue. Be wary of a standard offer that proposes the same size to every customer: oversizing a system without self-consumption or storage stretches the payback period.

Ask for a yield simulation (kWh per year), the estimated self-consumption rate and the electricity price assumed. With those three figures you can recompute the return yourself instead of trusting a generic "payback in eight years".

Other customers' feedback matters most for after-sales service: an installer's real quality shows two or three years after commissioning. Check online reviews, ask for two or three references in your commune or canton, and ask specific questions: were deadlines met, was the site left clean, how fast was the response when production dropped?

A serious company will put you in touch with past customers. A blanket refusal, with no explanation, is worth taking seriously.

A good installer offers a workmanship warranty of at least two years, on top of manufacturer warranties on panels (typically 25 years of performance) and inverters (10 to 15 years). Check they carry professional liability insurance covering damage to the building, for instance a leak after drilling through the roof.

Also settle the monitoring question: who watches the output, who alerts you if the inverter fails, and what response time is contractually promised? A system down for three summer months wipes out a year of savings.

A significant share of the cost can be covered by the Klimabonus, but the subsidy depends on precise evidence: an itemised invoice, a compliance certificate and the technical data of the installation. Agree in writing who prepares the file, who submits it on MyGuichet.lu and within what deadline.

Be careful with offers showing the subsidy already deducted: check who absorbs the difference if the grant is reduced or refused. The safe pattern is the classic one, the application stays in the owner's name and the quote shows the price before subsidy.

Slow down if the offer is valid "today only", if the deposit exceeds 30%, if the quote names no equipment brand or model, if the order is taken without a technical roof survey, or if the company has no physical address in Luxembourg.

Good signs, on the other hand: the installer inspects the roof or its survey photos before pricing, states constraints clearly (roof structure, asbestos, shading, consumer unit to be replaced) and tells you what is not included.

Verify the business licence, obtain three genuinely comparable quotes, review the sizing and the calculation assumptions, check warranties and insurance, and put the Klimabonus responsibilities in writing. Those five checks take a few hours and govern an installation meant to run for twenty-five years.