If you are putting solar on a commercial building in the North East, one piece of paperwork will shape your programme more than any other — and it is not the planning application. It is the G99 connection application to Northern Powergrid, the company that runs the local electricity network. Submitted early, it sits quietly in the background while the design work happens. Left until the panels are ordered, it becomes the reason a finished array sits on a roof, invoiced and idle, waiting for permission to switch on.
This post is the working detail behind the short version on our commercial solar page: what G99 actually is, who it goes to, how the process runs, and where it bites.
Who the application goes to
Northern Powergrid is the distribution network operator — the DNO — for the North East, Yorkshire and northern Lincolnshire, running the wires, substations and transformers that serve 3.9 million homes and businesses.
They are not your electricity supplier: you cannot switch away from them, and your supplier cannot speak for them. Anything that generates electricity and connects to their network — which is exactly what a solar array is — needs their agreement, because your export becomes a flow on infrastructure they are obliged to keep stable.
The rules for that agreement are set nationally, in the Energy Networks Association’s engineering recommendations. Two matter here: G98 for small systems, and G99 for everything else.
G98 or G99: where the line sits
G98 covers generation up to 16 amps per phase — about 3.7 kW on a single-phase supply, or roughly 11 kW across a three-phase one. At current module wattages, that three-phase ceiling is a couple of dozen panels: a domestic-scale system, in commercial terms. G98 installs can connect first and notify the network operator within 28 days of commissioning.
Cross the 16-amp line — and virtually every commercial array does — and you are in G99 territory, where the sequence flips: the application goes in first, Northern Powergrid assesses it, and connection happens only once it is approved. Almost every commercial rooftop system falls into G99’s smallest category, Type A, which covers generation below 1 MW and carries the lightest compliance requirements of the G99 classes.
That flip matters more than it sounds. An installer who treats the grid application as an afterthought is gambling your capital on the local network having spare capacity. Sometimes the gamble comes off. When it does not, the array waits — installed, paid for, and not yet permitted to operate.
What a G99 application involves
It is a technical submission, not a form-filling exercise, which is one reason it belongs with the contractor doing the electrical design. Ours includes the system’s generating and export capacity, the inverter details — type-tested equipment the DNO already recognises and assesses faster than novelties — a single-line diagram showing how the generation ties into your installation, and the site’s supply details.
Northern Powergrid then studies what your export would do to the local network — the transformer serving your area, the feeder your building sits on, the voltage rise your generation would cause on a sunny afternoon when local demand is low. What comes back is a connection offer: the terms on which the system can connect, any works the network needs first, and the costs if reinforcement is involved. Offers come with an acceptance window, so the moment to read one properly is the week it arrives, not the month after.
How long it takes — and why it goes first
The honest answer is that it depends on the state of the network around your building, which nobody can see from the outside. A straightforward application on an unconstrained network typically resolves in weeks. Where the local network is tight and reinforcement is involved, the process runs to months — and occasionally the reinforcement itself becomes the project’s long pole.
This is why the application is the first thing we submit once a design is settled — before panels are ordered, and in parallel with any planning work rather than after it. Most commercial rooftop solar in England is permitted development in planning terms, so on many projects the DNO, not the council, sets the critical path.
When the network says “not at full power”
A constrained network is not a refusal. Where full export cannot be accommodated, an export-limitation scheme under the G100 standard caps what the system pushes onto the network — measured and enforced at the connection point — while leaving what the building uses on site untouched.
Since a unit used on site is worth your full import price and an exported unit earns a fraction of it, an export-limited design often gives up remarkably little real value. For a daytime-heavy business, most of the generation was never leaving the building anyway. Installers who only build full-export systems tend not to mention this option; it has rescued more constrained-network projects than any other single tool we know.
Adding a battery changes the paperwork
An export-capable battery goes through the same G99 process as the array, and bolting one onto an existing system usually means reopening the connection agreement — the network operator assessed a solar array, and a battery changes what the connection can do. If storage is a realistic part of your plan, the cheapest moment to deal with it is inside the original application, not as a second application two years later. The full case for and against storage lives on our commercial battery storage page; the grid paperwork is one more reason to decide it early.
What this means for your project plan
The sequence that works, in the order it works:
- Survey and design first — system size and export capacity settled from your consumption data, because those numbers drive the application.
- G99 submitted at design stage — while the rest of the project is still on paper.
- Planning checked in parallel — usually permitted development; prior approval where the system tops 50 kW.
- Kit ordered once the offer terms are known — not before, unless you enjoy warehousing panels.
- Installation, then commissioning — with the connection agreement in place, the system exports legally from day one.
None of this is glamorous. It is procedural, deadline-driven, network-engineering work — which is why it suits an electrical contractor rather than a sales operation, and why we handle the application as part of every commercial project rather than listing it as an extra. Thirty-plus years of electrical contracting turns out to be decent preparation for filling in the DNO’s forms correctly the first time.
Planning a commercial array? Send us the building and your consumption data and we will tell you what the grid application is likely to involve for your site — including, honestly, whether your corner of the network is one of the tight ones. Get a commercial quote or call 01388 662659.