How to choose a mounting contractor for your solar PV plant

Why the choice of contractor matters

Mounting represents 8–15 % of a solar PV plant's CAPEX, but it determines the asset's reliability for the next 25–30 years. A torque that is off by 20 %, a cable laid against manufacturer specs, or a poorly crimped MC4 connector leads to yield losses that cannot be recovered. The selection of a mounting partner deserves the same scrutiny as the choice of modules or inverters.

10 criteria that actually decide

1. ISO 9001 and ISO 45001 from an accredited certification body (e.g. TÜV SÜD). A logo on a website is not enough — the management system must be audited.
2. References measured in MWp, not project count — installed capacity over the last 3 years.
3. In-house crews vs. subcontracting — a stable internal team delivers consistent workmanship.
4. Cross-border mobility — accommodation, transport, A1 posting, knowledge of local labour and tax rules.
5. Own mechanisation — pile drivers, drilling rigs, MEWPs. Renting them mid-project blows up the schedule.
6. Lost-Time Injury Rate (LTIR) — quality firms publish it openly.
7. Experience across substructure types — ramming, screw piles, ballast, rooftop.
8. QA/QC process — torque control, photo documentation, handover protocols.
9. Communication in the client's language — ideally SK/CZ/DE/EN.
10. Financial stability and liability insurance of at least EUR 1 million.

Questions worth asking in a tender

• How many MWp did you install in the last 12 months?
• What is your average and peak head-count on site?
• Which certifications are current and who is the certification body?
• What is your LTIR for the last 2 years?
• Which QA documents do you hand over at completion?

Conclusion

The cheapest bid is almost never the best. Investing in an experienced partner with genuinely audited processes pays back in faster delivery, better connection quality, and peace of mind once the plant goes live.