Technical Reports

Technical design reports for electrical installations: summary

A technical design report is the document that describes a low-voltage electrical installation when regulations do not require a full engineering project. It records the characteristics of the installation, the justifying calculations, the earthing system and the single-line diagram, so the administration and the utility can verify compliance without visiting the site. It accompanies the installation certificate: one certifies the work, the other describes how it is built.

Whether a report is enough or a full project is required depends on the size, use and risks of the installation. Simple, lower-power installations are usually documented with a technical design report signed by a licensed installer, while larger installations or premises open to the public require a project signed by a qualified engineer, normally with site supervision on top. At Captia we review each case first, then draft the documentation the specific procedure demands: legalisation, grid connection or subsidy files.

Both routes stay in-house. Our engineers are chartered industrial engineers, so they draft and sign technical design reports, industrial projects and certificates alike; and Captia is entered in the Registro Integrado Industrial as a low-voltage installation company, so the electrical installation certificate that accompanies the file is issued under our own registration. This work is frequently split across three companies (the installer, the engineering firm that signs, and whoever handles the filing), and the threshold between a report and a project is precisely where such a file changes hands. Here it does not.

Typical business cases include legalising solar installations for self-consumption, power upgrades in industrial premises, regularising old installations together with electrical reports, and preparing technical documentation for energy grant applications. The report is delivered ready to submit, as part of the full cycle covered by Captia Energy.

The 20 kW threshold and filing in the Valencian Community

The line between a technical design report and a full project is not a judgement call: it is set by ITC-BT-04 of the Spanish low-voltage regulation (Real Decreto 842/2002). Its list of installations that require a project includes industry in general above 20 kW installed (the threshold that decides most industrial files), single-family homes above 50 kW, residential buildings and non-public commercial or office premises above 100 kW per general protection box, premises open to the public regardless of power, outdoor lighting and swimming pools or fountains above 5 kW, and, with no power limit, premises with fire or explosion risk and operating theatres. Below those thresholds the installation is legalised with a technical design report.

The choice changes who signs and which procedure applies. In the Valencian Community filing is electronic only, with the territorial industry, energy and mining service of the province (Orden 14/2022, of 5 December): procedure 440 (SIA code 210646) for installations documented with a technical design report, using the MTD form and MTDALEX for extensions, and procedure 434 (SIA code 210644) for those requiring a project, together with the site supervision and completion certificate (CERINSBT) and, where the project carries no professional-body endorsement, the technician's responsible declaration (DECRESTE).

What that really means is that crossing the threshold does not add pages, it adds a role: a qualified engineer who has to be present from the first drawing to the completion certificate. Our engineers are chartered, so they sign the project, and being on the professional register also keeps the endorsement route open: a technician who is not registered can only file under the responsible declaration.

Self-consumption generation follows its own route: procedure 18168 for installed power of 10 kW or below and procedure 20714 above that figure. In both, the commissioning notice is filed electronically by the authorised installer only, and the procedure also enters the associated consumer in the administrative register of electricity self-consumption. Identifying the right door before drafting the documentation is what prevents rewriting it halfway through.

Verified on 9 August 2026 against ITC-BT-04 of the low-voltage regulation (Real Decreto 842/2002) and the sede.gva.es records for procedures 440, 434, 18168 and 20714. Thresholds, codes and forms are updated periodically, so check the text and record in force before filing.