Commissioning a Commercial Solar PV System: IEC 62446 Tests and Handover
Updated 23 October 2026 · SEO Dons Editorial
What does commissioning prove, and which documents come out of it?
Commissioning is the point where a finished system is inspected, tested and recorded before the owner accepts it. For a grid-connected commercial system, several records come out of it, each tied to a different rule:
| Record | Rule behind it | Usually produced by |
|---|---|---|
| Commissioning tests and inspection record | BS EN 62446-1 | The contractor's testers |
| Electrical Installation Certificate | BS 7671:2018+A4:2026 model forms | The electrical designer, installer and inspector |
| Commissioning evidence for the network operator | EREC G99 (Form A3 for Type A) | The installer, for the customer |
| Export limitation commissioning form, where used | EREC G100 | The installer |
| Health and safety file | CDM 2015, regulation 12 | The principal designer, passed to the client |
| MCS certificate and handover pack | MCS, systems up to 50 kW only | An MCS certified installer |
What do the IEC 62446-1 tests cover?
The IEC describes IEC 62446-1:2016 as defining "the information and documentation required to be handed over to a customer following the installation of a grid connected PV system". It also "describes the commissioning tests, inspection criteria and documentation expected to verify the safe installation and correct operation of the system". The UK adoption is BS EN 62446-1:2016+A1:2018, which BSI lists as current but under review.
Two points matter for a commercial buyer. First, the 2016 edition replaced IEC 62446 from 2009 and widened the scope "to include a wider range of system test and inspection regimes to encompass larger and more complex PV systems". Second, BSI says the standard "defines the different test regimes expected for different solar PV system types to ensure that the test regime applied is appropriate to the scale, type, and complexity of the system in question". For example, a hypothetical 400 kW roof should not be signed off on a test schedule written for a house.
The clause-by-clause list of tests sits in the standard itself, and this page does not reproduce it. Ask each bidder for its test schedule before award, showing for every string and inverter the test, the clause of the standard it follows, the instrument used, the reading and the pass criterion. Compare the schedules line by line, and ask which test regime the contractor is applying and why it suits a system your size.
The standard is one part of a series. The IET lists BS EN IEC 62446-2 for maintenance of PV systems and PD IEC TS 62446-3 for outdoor infrared thermography. If thermal imaging is part of acceptance, say so in the contract: the IET notes that when infrared thermography is used to check DC switch-disconnectors, the system should have been operating at a minimum ideal irradiance of 600 watts per square metre, so a survey on a dull day may tell you little.
What does BS 7671 add, and which edition should the certificate cite?
Historic England puts the requirement plainly: PV systems "must be inspected and tested to the requirements of British Standard BS 7671; as specified by the PV installer and as required by the DNO under the Engineering Recommendations G98 or G99 as relevant". The IET publishes model forms for BS 7671:2018+A4:2026, including the Electrical Installation Certificate.
The edition matters this month. The IET says the transition period for BS 7671:2018+A2:2022 ended on 15 October 2026, and that Amendment 2 "should no longer be referenced for new electrical installation work, project specifications, certification or compliance purposes". A specification written last year may still name it, so ask the designer to confirm the edition used on the design, the test schedule and the certificate.
What does the network operator need at commissioning?
The Energy Networks Association says a generator above 3.68 kW per phase comes under EREC G99 and that customers "must be able to demonstrate compliance with the requirements in the relevant document when generation is commissioned". MCS adds that G99 Type A covers 0.8 kW to less than 1 MW. Detail varies by operator, so treat UK Power Networks' published process as an illustration:
- Notice. The operator must be told the commissioning test programme "at least 28 days prior to commissioning (or 15 days before commissioning for Type A Power Generating Modules)".
- Witnessing. "The tests that UK Power Networks will witness depend on the EREC G99 Type (A - D) of Power Generating Module", and on what has been shown by other means such as type test reports.
- Record. Results go into the "Installation Document (Form A3 for Type A Power Generating Modules)".
- Parallel operation. Permanent operation in parallel is "not permitted until the commissioning tests have been completed and recorded".
- Unwitnessed commissioning. For fast-track small generation, the ENA says confirmation "shall be made no later than 28 days after commissioning (where commissioning tests and checks are not witnessed)" on Form A3-2. The Welsh Government's technical note gives the same 28 days where commissioning "does not have to be witnessed by the DNO".
- Export limitation. A scheme under EREC G100 needs its own commissioning tests form submitted. See export limitation and G100.
MCS notes that "a particular DNO may require you to use a different form", so confirm the forms with the operator named on the connection offer.
What must the handover pack contain, and what should insurers see?
Historic England says the handover pack should include "the warranty and basic system information such as the power rating of the arrays and inverters, the make and model of equipment, commissioning data, tests and results as well as operating and maintenance information". For a commercial system, add the items below.
- Drawings and specification. "Relevant plans, elevations and a specification" showing "the location of all equipment in the system", with fixing method and "cable types and routes".
- The health and safety file. Under regulation 12 of CDM 2015 the principal designer must prepare it, containing information "likely to be needed during any subsequent project", and at the end of the project it must be passed to the client. HSE adds that the client must ensure it is "made available to anyone who needs it for subsequent work at the site". See the CDM client duties guide.
- Certificates and forms. The Electrical Installation Certificate, the network operator's commissioning forms and, up to 50 kW, the MCS certificate, which MCS says arrives with "a handover pack" including "product details and workmanship warranty".
- Warranty documents. Check the start date of each; the warranties guide explains the layers.
Give the insurer the pack and the test results. RC62, the joint code of practice, was updated as a "practical guide for insurers and their clients" on procurement, ownership, operation and maintenance. For later testing, the IET notes that the 62446 series "recommends that inspection and testing intervals are no greater than those required for the AC system to which they are connected"; the maintenance guide covers the programme. Make delivery of the full pack a condition of acceptance in the contract.
The commercial PV installations guide shows where commissioning falls in a project, and you can send an enquiry through the quote form to put the same acceptance terms to several bidders.
Sources
- IEC, IEC 62446-1:2016, and BSI, BS EN 62446-1:2016+A1:2018, checked 22 October 2026.
- IET, checked 22 October 2026: BS 7671 amendments; model forms; Wiring Matters, April 2026.
- Energy Networks Association, connecting generation; UK Power Networks, witness testing; Welsh Government, grid connection technical note, checked 22 October 2026.
- MCS, becoming certified, notifying DNOs and solar panels, checked 22 October 2026.
- Historic England, PV maintenance, inspection and testing and PV designers and installers, checked 22 October 2026.
- legislation.gov.uk, CDM 2015 regulation 12; HSE, commercial clients; Solar Energy UK, RC62 announcement, checked 22 October 2026.
Common questions
Does commissioning include thermal imaging?
Not automatically. The IET lists outdoor infrared thermography in a separate part of the 62446 series, PD IEC TS 62446-3. If you want a thermal survey as part of acceptance, write it into the contract and require it to be done at a stated minimum irradiance.
Can the client or an independent engineer attend the tests?
Yes, if the contract says so. The network operator is given notice of the test programme and may witness its own tests, so ask for the same notice and a right to attend, and write both into the contract.
How soon must the network operator receive the paperwork?
Where commissioning is not witnessed, the ENA fast-track rules and the Welsh Government note both give 28 days from commissioning. Where the operator witnesses, its own process applies, and some operators ask for the test programme in advance.
When are the next tests due after handover?
The IET says the 62446 series recommends intervals no greater than those for the AC system the PV connects to. The commissioning record becomes the baseline for later periodic tests.