For a UK manufacturer, the day a rooftop solar array starts producing electricity is not the end of the project. It is the point at which the factory should receive evidence that the installation has been tested, connected appropriately, documented and handed over to the people who will operate it.
Without a clear commissioning and handover process, a business can inherit missing electrical records, unclear warranty responsibilities, restricted monitoring access or unexpected problems when it needs to maintain the roof. This practical checklist is for factory owners, finance directors, facilities managers and procurement teams taking delivery of a commercial solar PV system.
If you are still assessing whether solar is right for your site, begin with our Solar Panels for Factories UK guide. This article focuses on the acceptance and handover stage, rather than project sizing or headline savings.
1. Agree the acceptance criteria before installation
Commissioning should not be an informal demonstration that the inverters switch on. The contract should define which tests, documents, training and remedial works are needed before practical completion, final acceptance and any associated payment milestone.
Ask the installer to supply an agreed acceptance schedule. It should identify the party responsible for each deliverable, the expected completion date and the person authorised to sign it off. A commissioning checklist is particularly important for a factory where an electrical shutdown, roof access or switchgear intervention could disrupt production.
Practical distinction: physical completion, permission to operate in parallel with the distribution network, successful commissioning and final commercial acceptance are related but are not necessarily the same milestone. The contract and DNO requirements should make the distinctions clear.
2. Obtain the as-built electrical and roof documentation
Factory facilities teams should not have to reconstruct the design after the contractor leaves. The handover pack should include accurate, legible as-built drawings and equipment schedules showing what was actually installed, not simply what appeared in the original quotation.
- Solar module make, model, quantities and final array layout, including roof zones and access routes.
- Inverter and optimiser details where applicable, serial numbers, ratings and firmware or configuration records.
- AC and DC single-line diagrams, cable routes, protective devices, switchgear interfaces and isolation points.
- String schedules, relevant labels, circuit identification and monitoring or communications architecture.
- Structural and roof-interface records, fixing-system details, relevant warranties and any changes agreed during construction.
The exact documents depend on the system design and the applicable standards. BS EN 62446-1 addresses documentation, commissioning tests and inspection for grid-connected PV systems. Ask the designer or independent engineer which version and additional standards apply to your project.
Where the factory uses LV/HV transformers or complex switchgear, our factory transformer and electrical-readiness guide explains why the interface deserves attention before the project reaches this stage.
3. Review electrical inspection and test evidence
A competent electrical professional should carry out and record the inspections and tests appropriate to the installation, including relevant PV DC checks, AC installation checks, polarity and continuity checks, protective measures and functional verification. The detailed test scope depends on the system, applicable wiring and PV standards and the engineer’s design.
Ask for the actual signed test schedules and results, not a generic statement that the installation “passed”. Check that any defects or departures are recorded, with clear responsibility and dates for correction. If infrared inspection or performance testing was specified in the contract, obtain the results and note the conditions under which they were taken.
Electrical commissioning also needs to consider existing industrial equipment. A site with drives, capacitors or sensitive machinery may need additional review. See our factory solar power-quality guide for harmonics, power factor and voltage issues.
4. Confirm the DNO connection and G99 close-out
Many commercial and industrial PV systems follow Engineering Recommendation G99. The local distribution network operator (DNO) may require specific protection settings, compliance evidence, tests or witnessed commissioning. Requirements vary by generating-module type and the connection offer.
National Grid Electricity Distribution’s G99 procedures confirm that installers must undertake relevant commissioning tests and that the DNO may require witness testing. For some connection types, operational notifications and commissioning forms are also required.
Before sign-off, ask for the accepted connection offer and any operating restrictions, the relevant compliance and commissioning forms, evidence of required notifications, and confirmation that any export-limitation equipment has been tested where applicable. Do not assume that a successful inverter start-up means every DNO condition has been satisfied.
Our separate factory solar DNO and G99 guide explains the earlier application process in more detail.
5. Check emergency isolation, fire information and safe roof access
The factory should know how to isolate the solar installation safely, who is authorised to do so, and what information is available to emergency responders and maintenance contractors. PV circuits can remain energised in daylight even when parts of the system have been switched off, so instructions must reflect the actual design and hazards.
Obtain the site-specific emergency plan, isolation diagrams, safety labels and operating instructions. Review whether the fire-risk assessment and insurer information need updating. Roof access arrangements should cover fragile rooflights, fall protection, safe routes and the ability to inspect or repair both the solar array and the underlying roof.
The Health and Safety Executive’s roof-work guidance stresses planning, competent workers and controls for roof edges, openings and fragile surfaces. Our factory solar fire-safety checklist explores the relevant design and operational questions.
6. Take control of the monitoring account and data
Do not leave monitoring access tied only to an installer’s personal account. The factory should have documented ownership or agreed administrator rights, named authorised users, training, alert contacts and a process for transferring access if the service provider changes.
Check that the portal reports plausible solar generation and inverter status, and that any import/export data comes from correctly identified meters. A generation dashboard does not on its own prove savings against the electricity bill.
Agree the baseline, reporting intervals, fault-notification thresholds and responsibilities for investigating underperformance. Our factory solar monitoring and savings-verification guide sets out the financial measurement process in detail.
7. Collect warranties, O&M manuals and support contacts
A factory solar system includes multiple components with different warranty terms. Ask for the module product and performance warranties, inverter warranty, mounting-system information, workmanship warranty, applicable roof warranties and any operations-and-maintenance agreement.
Check the exclusions, registration requirements, claims route, labour and access costs, response times, spare-parts arrangements and what happens if an equipment manufacturer or installer changes ownership. A “25-year panel warranty” does not necessarily mean the entire installation has 25 years of comprehensive cover.
Request an operations-and-maintenance (O&M) manual covering routine inspections, cleaning decisions, safe access, electrical testing, monitoring, fault escalation and shutdown/restart procedures. See our commercial solar maintenance guide for UK factories.
8. Train the people who will operate the system
Arrange a practical handover session for facilities, engineering, health-and-safety and finance representatives. The training should show the actual isolation points and alarm procedures, how to view monitoring data, how to report a fault and whom to contact before planned roof or electrical works.
Keep a signed training attendance record and a concise one-page operating summary accessible to relevant staff. Do not treat a handover demonstration as authorisation for unqualified personnel to carry out electrical work.
If installation has to be phased around production, review our factory solar installation and production-downtime checklist.
9. Resolve snagging and agree the final acceptance record
Before releasing a contractually linked final payment, confirm that the installer has supplied the agreed documents and test evidence, completed any required commissioning, resolved critical defects and provided a dated list of minor outstanding items.
A sensible acceptance record includes the commissioning date, equipment inventory, unresolved snagging, responsible persons, target closure dates, warranty commencement dates, monitoring access and any performance or availability obligations. Commercial terms differ: review the signed contract rather than assuming a standard retention percentage or automatic right to withhold payment.
For multi-roof or phased projects, record which sections have been accepted and which remain under construction. That prevents confusion about responsibility for equipment that is generating electricity but has not yet reached final handover.
10. Printable factory solar handover checklist
- Contractual acceptance criteria and named sign-off responsibilities agreed.
- Final as-built array drawings, single-line diagrams and equipment schedules delivered.
- Applicable electrical inspection, test and commissioning records signed.
- DNO/G99 conditions, required forms and export limits documented.
- Emergency isolation, labelling and fire information handed over.
- Roof access, fragile-surface risks and maintenance routes reviewed.
- Monitoring administrator access, alerts and raw-data arrangements transferred.
- Warranties, registration evidence, O&M manuals and support contacts received.
- Relevant factory personnel trained, with attendance recorded.
- Snagging list, closure dates and final acceptance record signed.
This is a practical procurement aid, not a substitute for the applicable standards, competent engineering judgement or the project’s contractual and DNO requirements.
Frequently asked questions
What is the difference between commissioning and handover?
Commissioning establishes, through relevant checks and tests, whether the installed system operates as intended. Handover transfers the documentation, knowledge, access and agreed responsibilities needed for the owner to operate and maintain it. A project may require both before final acceptance.
Does the DNO need to witness every commercial solar installation?
No. Whether witness testing is required depends on the connection and the DNO’s requirements. Confirm the position in the connection offer and arrange testing accordingly.
What if the installer has not provided complete as-built drawings?
Record the omission against the contract’s document schedule, request corrected records and agree how it affects the acceptance milestone. Do not substitute old design drawings for the actual installation without checking them.
Can factory staff maintain the panels themselves?
Only within their competence and under a safe system of work. Electrical testing, roof work and other specialist activities require appropriately competent people and controls. Refer to the O&M manual and site risk assessments.
Conclusion: make handover part of the investment case
For a factory, the value of solar depends on safe operation, reliable evidence, maintainable equipment and clear ownership of the system long after the installation team has left. A disciplined commissioning and handover process helps protect that value and gives the facilities and finance teams a reliable starting point.
Planning a UK manufacturing solar project? Explore our factory solar authority guide or contact Commercial Solar Systems to discuss the project scope and the handover evidence you should expect.
