An inspection is worth having at three moments: before buying a house that has an array, when generation drops, and periodically on an array you own. In all three cases the job is the same: confirm the installation is safe, is producing what it should, and has the paperwork that proves it was done and connected lawfully.
What a solar survey or inspection actually measures
String voltages and currents against the expected values for the conditions, insulation resistance, the state of the DC isolator and every connector, earthing and bonding, the inverter's fault log, the condition of the mounting and its weathering, and the state of the roof under and around the array. A thermal look at the panels can show a hot cell or a failed bypass diode that nothing else reveals. The output is a report with figures in it, not an opinion.
The paperwork that should exist
An electrical installation certificate for the new circuit, the commissioning record with the string test results, the notification or connection agreement with the distribution network operator, the certification paperwork if the system claims export payments, the warranty registrations, and a manual with the string layout and the isolation points. Missing paperwork is not automatically dangerous and it is always a problem: it complicates export payments, insurance and selling the house, and it is what a buyer's solicitor will ask for.
Solar DNO notification and the maximum solar on single phase UK supplies
A generator connected to the network is either notified after connection or applied for before it, depending on its size and the supply. Small domestic installations are normally notified under the simpler route; larger installations and anything on a constrained network need permission first. A single phase supply has a limit on what can be connected without a prior application, and an installer who exceeded it without asking has created a problem that surfaces at the worst possible moment. The record of that notification is a document you should hold.
Buying a house with an array
Ask for all of the above before exchange, plus who owns the panels. If they are under a lease or a third party ownership agreement, that agreement runs with the roof and you are inheriting it, including whatever it says about re roofing and access. If the array is owned outright, check whether the warranties are transferable and whether export payments can be transferred into your name, because neither happens automatically.
Questions people ask about solar panel inspection
What should a solar inspection report contain?
Measured string voltages and currents, insulation resistance, the condition of isolators and connectors, earthing, inverter fault history, the mounting and roof condition, and a comparison of generation against expectation. Figures rather than adjectives.
What paperwork should a UK solar installation have?
An electrical installation certificate, commissioning and string test records, the network operator notification or connection agreement, certification documents where export payments apply, warranty registrations and a manual with the string layout.
What if the paperwork is missing?
An inspection can establish that the installation is safe and working, but it cannot recreate a historic certificate. Expect complications with export payments, with insurers and with a buyer's solicitor, and price an inspection and any remedial certification into the decision.
Do I need a DNO certificate for solar panels?
Yes. Small installations are normally notified after connection under the simpler route and larger ones need permission first. The document recording that is part of the installation's paperwork and should be handed over with it.