Commercial solar panel installation
What happens on site and in the background, in what order, and the paperwork worth keeping somewhere safe.
The question businesses actually ask isn’t whether solar works. It’s what happens to the building and the operation while it goes in, and whether anyone has to stop working. The short answer is that most of a commercial installation happens on the roof and in correspondence you never see, and the disruption inside the building comes down to a single planned interruption. Here’s the sequence from first survey to switch-on.
Survey and design
A surveyor looks at the roof structure and covering, checks fixings and condition, maps shading across the day, and reviews your electrical intake and consumption data. Out of that comes a layout, an inverter specification and a generation estimate.
Be wary of anyone willing to quote without visiting. Roof structure and access are two of the three things that most affect what a project costs, and neither can be assessed from an aerial photograph. The third is your grid connection, which is the next step.
Permission to connect
Anything generating alongside the grid needs the district network operator to know about it, and the route depends on size. Smaller installations fall under the G98 arrangement, which allows the system to be fitted and the network operator notified afterwards within a set period. Larger installations, which covers most commercial projects, go through G99, where the application is submitted and approval received before any equipment goes up.
The threshold is set in terms of export current per phase rather than panel capacity, so it depends on your supply arrangement as well as the system. Your installer establishes which route applies and handles the submission. G99 responses take time, and where the local network needs work to accept your export there may be conditions or costs attached, so ask where the application stands before scaffolding is booked.
Planning permission, usually a short conversation
Most commercial rooftop installations sit within permitted development rights, provided panels don’t project far from the roof surface and the building isn’t listed or in a conservation area. Ground-mounted arrays are a different matter and often do need an application.
Your installer confirms which applies during design. For the majority of commercial buildings this stage takes a phone call rather than a planning consultant.
The work on site
Access equipment or scaffolding goes up first. Mounting rails fix to the roof structure, panels attach to the rails, and cabling runs back to the inverters, which usually sit in a plant room or on an internal wall near your intake. Almost all of this happens outside the working envelope of the building.
The one moment that touches your supply is the final connection into the distribution board, which needs a planned shutdown. It’s normally a matter of hours and it gets scheduled around your operation, often first thing or at a weekend. Time on the roof scales with system size, from a couple of days on a modest array to a fortnight or more on a large industrial roof.
Commissioning and the paperwork that matters later
The system is tested, energised and handed over with a document pack. Depending on system size that includes installation certification, the confirmation from your district network operator, electrical and commissioning certificates, equipment warranties and access to the monitoring platform.
File all of it properly. When you come to register for export payments, a supplier will ask for evidence of certification and the grid connection, and reconstructing that years later means chasing an installer who may have moved on. The export tariff guide covers what’s needed and what to do when the paperwork has already gone astray.
What to do after switch-on
Three things, none of them onerous. Watch the monitoring against the design estimate through the first month or two, while the installer is still close to the job and the workmanship warranty is fresh. Set up the export tariff, which is separate work from the installation and needs an export MPAN and an application to a supplier.
And revisit your electricity contract. Generating on site changes your consumption profile, sometimes substantially, and a renewal priced against your historical usage won’t reflect what you now actually buy. That’s a conversation worth having before the next renewal window rather than after it, and it’s one we handle for clients alongside the renewal timing itself.
Questions worth asking an installer
Which connection route applies to this system and who is submitting the application. What the generation estimate is based on, and whether it used our own consumption data. What is included in the price and what would come back as a variation. Who provides the certification at handover, and what exactly we receive. What the workmanship warranty covers as opposed to the product warranties. And whether the export registration is part of the job or left with us.
That last one catches people out regularly. A number of installations end up generating for years with the export side never set up, simply because everybody assumed somebody else was dealing with it.
Frequently asked questions
How long does commercial solar installation take?
Typically a few weeks from go-ahead to generation, with only a small part of that spent on site. Survey, design and the network operator application account for most of the elapsed time.
Will our power be switched off during installation?
Once, briefly, for the final connection into your distribution board. It is planned in advance and usually scheduled outside your busiest hours. The rest of the work does not affect your supply.
What is the difference between G98 and G99?
They are the two routes for connecting generation alongside the grid. Smaller installations use G98 and can be fitted first and notified to the network operator afterwards. Larger installations use G99, where approval must be obtained before anything is installed. The threshold is based on export current per phase.
Do we need planning permission for rooftop solar?
Usually not. Most commercial rooftop systems fall under permitted development, provided panels sit close to the roof surface and the building is not listed or in a conservation area. Ground-mounted arrays more often need an application.
Can panels be installed on any commercial roof?
Most steel-framed commercial roofs are suitable. Fragile coverings, asbestos and roofs near the end of their life all need addressing first, which the survey identifies before anything is committed.
What documents should we receive at handover?
Installation certification appropriate to the system size, confirmation of the grid connection from your network operator, electrical and commissioning certificates, warranties and monitoring access. These are what a supplier asks for when you register for export payments.
Does the roof need to face south?
South is ideal, though east and west facing arrays perform well and spread generation across more of the working day, which often suits a business consumption pattern better than a single midday peak.
Who deals with the network operator?
The installer normally prepares and submits the application. It is still worth knowing where it stands, because the outcome can affect timing, cost and how much export the system is permitted.
What happens if the network cannot accept our export?
The network operator may approve a smaller system, impose an export limit, or quote for reinforcement works. Export limitation devices are a common solution and let a system proceed while capping what leaves the site.
Do we need scaffolding?
Some form of safe access is always needed. Whether that is scaffolding, a mobile platform or roof edge protection depends on the building, and it should be priced within the quote rather than added later.
When should we set up the export tariff?
As soon as the system is commissioned. Export payments are not backdated, so generation exported before registration earns nothing.
Should our electricity contract change after installation?
Your consumption profile will change, so the next renewal should be priced against your new usage rather than your historical figures. It is worth reviewing before the renewal window rather than after.
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