A good commercial solar installer should coordinate most of the process for you. Not every part of it is completed by the same person, and knowing who is responsible for what before the project starts is the difference between a job that runs and a job that stalls.
There are several separate pieces of administration on a commercial solar project: the DNO application, the structural engineer’s report, planning checks, electrical certification, commissioning documents and handover paperwork.
Some are ours. Some need a structural engineer, a planning authority, or the Distribution Network Operator.
Here is how it actually works, and roughly how long each part takes on the projects we run across Hertfordshire, Bedfordshire, Buckinghamshire and North London.
Key Takeaways
- Most businesses should not need to manage the technical paperwork themselves.
- The DNO application is normally prepared and submitted by the solar installer or electrical designer.
- On our patch the relevant DNO is usually UK Power Networks. A 50kW commercial system currently takes us around 10 weeks for approval.
- G98 is connect-then-notify within 28 days. G99 is apply and wait for approval before you install. They are frequently confused.
- Planning permission and DNO approval are entirely separate processes, and planning is often the longer of the two.
- Synergy will not install any commercial system until both the DNO approval and the structural engineer’s report are in. No exceptions.
- A standalone G99 application typically costs between £450 and £1,200 depending on complexity.
What Is the Difference Between G98 and G99?
These are the two engineering recommendations governing how generation connects to the public distribution network, and they get mixed up constantly.
| G98 | G99 | |
|---|---|---|
| Applies to | Up to 16A per phase, roughly 3.68kW single-phase, around 11kW three-phase | Anything above those limits |
| Process | Connect first, notify the DNO within 28 days of commissioning | Apply and receive approval before the system is installed or energised |
| Typical use | Domestic and very small commercial | Almost all commercial installations |
The practical consequence is significant. Under G98 you can get on with the job. Under G99 you cannot install until the DNO says yes, and that wait sits on your programme whether you planned for it or not.
For most commercial buildings, G99 is the route.
How Long Does a DNO Application Actually Take?
This is the question nobody answers with a real number, so here are ours.
| System | DNO | Approval time |
|---|---|---|
| 50kW commercial rooftop (around 110 panels) | UK Power Networks | Approximately 10 weeks |
| 228.8kWp – Wenzel’s the Bakers, Watford | UK Power Networks | 14 weeks |
UKPN cover most of our service area and, in our experience, they are among the more straightforward DNOs to deal with.
Smaller commercial systems can move considerably faster. Larger and more complex connections take longer, and the timescale is not always predictable, it depends on the size of the system, the existing supply to the building, and what is happening on the local network.
Worth sitting with – Fourteen weeks of DNO approval against two weeks of physical installation on the roof. On a commercial project, the paperwork is almost always the longer part of the job.
What Can the DNO Actually Impose?
More than most people expect, and this is why the application is a design question rather than an administrative one.
The DNO can require an export limitation, and on constrained parts of the network that frequently means zero export, every unit you generate has to be consumed on site. They can require specific G99 protection settings so the system disconnects within defined voltage and frequency limits. On some sites there can be a financial cost to connect at all.
Locations with existing generation nearby, such as sites close to wind turbines, tend to attract more conditions rather than fewer.
None of that is a reason not to proceed. It is a reason to find out early, because every one of those conditions changes the design and some of them change the price.
Why Export Limitation Is a Bigger Job on Commercial Than Domestic
On a domestic installation, export limitation is usually straightforward. Most domestic hybrid inverters are type-tested G99 devices with the capability built in. We supply the certificate and the datasheet and that is largely that.
Commercial is different, and it is worth understanding why.
We use Solis string inverters on larger commercial systems. They do not have integrated export limitation in the way a domestic hybrid does, and that is architecture rather than an omission.
- Export has to be measured at the point of connection with the network, not at the inverter. On a house the inverter is a few metres from the consumer unit. On a commercial building the incomer is often in a different plant room entirely.
- Domestic hybrids already have the metering hardware, because they need to watch the grid connection anyway to decide whether to charge the battery or export. Export limitation is a firmware feature sitting on top of hardware that is there for another reason.
- Most importantly, commercial systems often run more than one inverter. Wenzel’s ran two Solis 100kW units. No individual inverter can see total site export, so no individual inverter can limit it. You need a central controller aggregating both and commanding them together.
- A compliant export limitation scheme has to respond fast, typically sub-second, which means a hardwired link rather than anything wireless.
In practice that means a separate export power manager, dedicated current transformers at the origin, an enclosure, and a hardwired data run from the switchboard back to the inverters.
On a retrofit, that cable route can be one of the more expensive parts of the whole job. It is also the part that gets missed at quoting stage, because it looks like a setting rather than an installation.
Why Being Electricians First Matters Here
An export limitation scheme is predominantly an electrical installation job. Switchgear, CTs, containment, cable routes, protection, commissioning.
This is where the Synergy group structure earns its keep. Synergy Group Solutions is an established commercial electrical contractor with NICEIC-approved electricians. Synergy PV Renewables designs and installs the solar. Both sit under the same roof with the same management team.
For a client, that removes a coordination problem that causes real delays elsewhere. The usual alternative is a solar company and a separate electrical contractor, with the client managing both. That works until it doesn’t, and where it fails is at the interface. The electrician may not have the solar knowledge. The solar installer may not be able to specify the electrical work precisely enough for someone else to price and deliver it.
Doing both in-house also tends to be more competitive, because there is one management overhead rather than two.
Does Every Commercial Solar Project Need Planning Permission?
No. Grid approval and planning permission are completely separate, and a project can need DNO approval where no planning application is required at all.
Many commercial rooftop installations fall within permitted development rights, provided the relevant conditions are met. It becomes more complicated with listed buildings, protected settings, conservation considerations, unusual mounting arrangements, ground-mounted systems, or anything outside permitted development limits.
We check the position rather than assume it. Equally, we do not tell every client that planning is automatically covered simply because the panels are going on a roof.
On ground mounts and areas of outstanding natural beauty, planning is usually the longest stage of the whole project
Longer than the DNO. Longer than anything else. It can run to six months.
The Sequencing Mistake That Costs Businesses Months
This one is worth reading twice, because we see it regularly.
A business submits a planning application. They wait, sometimes up to six months. Planning is approved. Only then do they start the DNO application, which triggers another ten to fourteen weeks.
Those two processes did not need to run in sequence. They could have run alongside each other, and the project could have been energised a full quarter earlier.
We run the DNO application alongside planning as a matter of course, and we will do it before the job has been formally awarded.
What we tell clients – We are happy to prepare and submit the DNO application on your behalf. It does not tie you to using us as your installer, and it does not commit you to installing at all. What it does is start the clock. If you go elsewhere afterwards, the approval still stands and you have saved yourself three months.
Not every installer will tell you that the DNO application does not lock you in. It is worth knowing regardless of who you end up using.
Who Arranges the Structural Engineer?
We do. The assessment itself is completed by a suitably qualified structural engineer, we work with named partners including James Longwell, and the report considers the added weight of the array and mounting system along with lifetime loads, including snow loading.
Our position is simple and it is not negotiable:
The rule – Every commercial installation gets a structural engineer’s report. No exceptions. We treat it as exactly the same class of gate as the DNO application, neither approved, no install.
A report the client already holds for other works does not count. A sign-off for a refurbishment says nothing about several tonnes of ballasted solar sitting on the roof for the next twenty-five years.
We pass the engineer’s fee straight through to the client at cost, with no markup. That keeps the responsibility clear: we design the solar installation, the structural engineer signs off the structure.
What Does the Paperwork Cost?
On a project we are delivering, the DNO application is included. We allow a nominal amount of time for the admin and compliance work in the overall price.
Where we are asked to prepare and submit a G99 application on its own, for example on a tender we have not been awarded, or for a client who wants the clock started before committing, a standalone application typically ranges from £450 to £1,200 depending on the complexity of the site and the amount of design work the application requires.
The structural engineer’s fee is separate and passed through at cost. On a straightforward commercial roof it is usually in the region of £1,200, but it depends on the building.
Ask any installer to break these out. If one quotation includes the structural report and another assumes you are arranging it, the two are not comparable.
What Should Be in the Handover?
By the time the system is running you should not simply be handed an inverter password.
Depending on the project, the handover pack should bring together electrical certificates, commissioning records, DNO correspondence, structural documentation, system drawings, manufacturer documentation, warranty information, monitoring access, operating information, and MCS documentation where applicable.
Remote monitoring is included as standard on our installations rather than treated as an optional extra. If we have installed the system, we want the client to be able to see what it is doing, and we want to be able to see it too.
What to Confirm Before You Sign
- Who prepares and submits the DNO application?
- Are any DNO fees included in the quotation?
- Who arranges the structural engineer, and is the fee included or separate?
- Who checks whether planning permission is required, and who handles the application if it is?
- Will the DNO application be run alongside planning, or only after it?
- Who completes the electrical certification and commissioning?
- Is remote monitoring included?
- If export limitation is required, who is doing the electrical work and is it priced?
- Which parts of the process remain my responsibility?
Those are straightforward questions and a commercial proposal should give you straightforward answers.
Who Should Coordinate All of This?
One company should be taking responsibility for the project, even where specialist third parties are involved. The structural engineer has their role, the DNO has theirs, the planning authority may have theirs, but the client should not be the one working out how the pieces fit together.
At Synergy PV Renewables we manage the solar and electrical design, coordinate the project requirements, and make it clear where a third-party specialist owns a specific part of the work.
If you are considering commercial solar in Hertfordshire, Bedfordshire, Buckinghamshire or North London and want to understand what approvals your site will need, call 01442 921055 or email hello@synergypvrenewables.co.uk.
We will tell you what needs doing, who needs to do it, and what has to be in place before installation starts.
FAQs
How long does a DNO application take for commercial solar?
On our projects with UK Power Networks, a 50kW commercial system currently takes around 10 weeks. Our 228.8kWp installation at Wenzel’s the Bakers in Watford took 14 weeks. Timescales vary with system size, the existing supply and local network conditions.
What is the difference between G98 and G99?
G98 covers generation up to 16A per phase, roughly 3.68kW single-phase, and allows you to connect first and notify the DNO within 28 days. G99 covers anything larger and requires DNO approval before the system is installed or energised. Most commercial installations fall under G99.
Do I need to apply to the DNO myself?
Normally no. The application relies on technical information about the generation equipment, electrical design, protection settings and connection arrangement, so the installer or electrical designer should prepare and submit it.
Does submitting a DNO application tie me to that installer?
No. The approval relates to the connection, not the contractor. You can submit an application, receive approval, and then choose a different installer, or choose not to proceed at all. Starting it early is usually the single best thing you can do for your programme.
Does DNO approval mean I have planning permission?
No. They are separate processes. DNO approval concerns connecting generation to the electricity network. Planning concerns development of the building or land. On ground-mounted systems and sites in protected areas, planning is often the longer of the two.
What happens if the DNO limits my export?
The system and connection arrangement may need adjusting to meet the DNO’s requirements, and on some networks that means zero export. On a commercial system that usually requires a separate export limitation scheme with its own metering, controller and cabling — which is why grid requirements should be understood during design rather than after.
Who pays for the structural engineer?
The client, but at cost. On Synergy commercial installations a structural engineer’s report is mandatory and the fee is passed directly through without markup.
