Choosing the right solar installer matters as much as choosing the right panels. A poor installation can void warranties, fail safety inspections, underperform by 15–20%, and create costly remediation bills. This solar installer vetting guide gives you a practical 17-point checklist for the UK and EU in 2026, built around the certifications, questions, and red flags that experienced buyers use.
Mandatory Certifications and Registrations
Before inviting any installer to quote, verify the following:
- 1. MCS certification (UK) — Microgeneration Certification Scheme accreditation is required to access SEG tariffs, the ECO4 scheme, and most council grants. Verify at mcscertified.com — check the specific company, not just a name.
- 2. NICEIC or NAPIT registration (UK) — for the electrical installation elements. An MCS installer should also hold a relevant electrical competency registration.
- 3. RECC membership — the Renewable Energy Consumer Code provides an additional dispute resolution mechanism and requires members to comply with fair trading standards.
- 4. EU equivalent: EPBD-compliance certification — in EU member states, look for installer certification under national energy performance schemes (e.g., RGE QualiPV in France, SOLARPARTNER in Germany, Qualinstal in Italy).
- 5. Public liability insurance (minimum £2m UK / €2m EU) — request a copy of the certificate and check the expiry date. Do not accept verbal assurances.
- 6. Professional indemnity insurance — separate from public liability; covers design errors and specification mistakes.
Experience and References
- 7. Years trading and installations completed — ask specifically how many residential systems of similar size to yours they have installed in the past 24 months. A firm with 200 commercial installs but only 10 residential may not be the best fit.
- 8. Verified reviews — Trustpilot, Google, and Which? Trusted Traders provide independently verified reviews. Ask for three customer references you can contact directly.
- 9. Local presence — an installer based within 50 miles is more likely to respond quickly to post-installation issues. Distant firms with no local sub-contractors are a support risk.
Equipment and Design Quality
- 10. Panel and inverter brands specified — insist on a named specification. Tier 1 Bloomberg panel status and inverter brands with EU/UK service centres (Fronius, SMA, SolarEdge, Enphase, Sungrow, Growatt) are appropriate benchmarks. Be wary of unbranded or "own-label" equipment.
- 11. IEC 62446-1 commissioning report — this standard defines the documentation, testing, and verification required at handover. Ask whether the installer issues an IEC 62446-1 compliant commissioning report as standard. Many do not unless asked.
- 12. Shading analysis provided — any credible design should include a shading analysis (via software such as Solargis, PVsyst, or nearmap). If no shading analysis is mentioned, the design is incomplete.
- 13. System yield estimate and methodology — ask what software and irradiance dataset they use to model system yield. PVGIS (EU Joint Research Centre) is the standard reference for the UK and EU. Estimates more than 10% above PVGIS baseline for your postcode warrant scrutiny.
Contracts and Payments
- 14. Payment milestone structure — a reputable installer will accept a deposit of no more than 25–30%, with the balance payable on satisfactory installation and commissioning. Never pay in full upfront.
- 15. Written contract before work begins — this should specify equipment by make and model, installation date, total price, and warranty terms. Verbal agreements are unenforceable.
- 16. Workmanship warranty term — 5 years as a minimum for the installation itself, separate from manufacturer product warranties on panels and inverters.
Post-Installation Support
- 17. Monitoring setup and handover — confirm the installer will configure and demonstrate the monitoring system at handover, and that you have login credentials for the portal. Systems left unmonitored are systems with undetected faults.
Five Red Flags That Should End the Conversation
- Pressure selling or time-limited discounts — "sign today for the special price" is a sales tactic, not a genuine offer. Reputable installers do not pressure customers.
- Cannot produce MCS or equivalent certification on request — check it yourself; do not accept a promise to email it later.
- Yield estimates significantly above PVGIS baseline — inflated yield projections are used to shorten apparent payback periods and close sales. They are a form of mis-selling.
- Unbranded or grey-market equipment — panels or inverters with no identifiable manufacturer or no EU/UK service infrastructure are a warranty and support risk.
- Requests for majority or full payment upfront — this removes your leverage entirely if the installation goes wrong.
Key Takeaways
- MCS certification, NICEIC/NAPIT registration, and RECC membership are the UK baseline — verify each independently online.
- Demand a named equipment specification, shading analysis, and IEC 62446-1 commissioning report as standard deliverables.
- Pay no more than 25–30% deposit; insist on a written contract with model-specific equipment listed before work starts.
- Yield estimates more than 10% above PVGIS baseline for your location warrant scrutiny and explanation.
- Pressure tactics, upfront full payment requests, and unbranded equipment are disqualifying red flags.
A thorough vetting process takes a couple of hours and could save you thousands. The installers who pass this checklist are generally confident in their work and welcome the scrutiny.