Export limitation: the G100 route that gets a bigger job connected on a constrained grid

You have quoted a customer for a 7kW-plus solar array with battery storage, they have signed, and then the DNO connection comes back with a problem: the local network cannot accept that much export. On some feeders the answer is reinforcement - a network upgrade that adds months and a cost nobody budgeted for. The job stalls, the customer cools off, and the deposit you took starts to feel like a liability rather than a win.

Export limitation is the route around that wall. Instead of exporting everything the system can generate, you cap what the site is allowed to push back to the grid, and manage the rest on site. It is how a growing installer keeps larger battery-and-solar jobs moving on networks that would otherwise say no.

What export limitation actually does

An export limitation scheme monitors what the site is exporting at the connection point and holds it below the level the DNO has agreed. If generation starts to push past that limit, the scheme responds automatically - typically by ramping the inverters down, or by diverting the surplus into on-site load such as charging a battery. The customer still gets the full benefit of self-consumption from a larger system; the grid just never sees more than the agreed number.

The framework for this is ENA Engineering Recommendation G100, Issue 2 Amendment 2, the industry standard for export and import limitation schemes. The current issue of G100 broadened the scope to cover import limitation as well as export, which matters for battery installs where charging from the grid could otherwise breach an agreed import capacity. In practice, the DNO is agreeing to a managed connection rather than an unmanaged one, and the scheme is the mechanism that keeps you inside the agreement.

Why it gets a stalled job connected

The reason export limitation is worth understanding as an operational tool, not just a technical one, is what it does to the connection decision.

A full-export application on a constrained feeder can be refused outright, or offered only with network reinforcement attached. Reinforcement is the killer: it adds cost and can push the connection date out by months, which for a signed job means a customer waiting through a season they expected to be generating in.

An export limitation scheme changes the calculation. Because the network only ever sees the capped export figure, the assessment is against that lower number, not the system's full generating capacity. National Grid's guidance on customer export limitation schemes sets out how these are used to connect systems that would otherwise exceed what the network can accept. Many DNOs will progress a G99 application more quickly when it arrives with a compliant export limitation scheme already specified, because it removes the need for a lengthy network study of a full-export case.

So the practical sequence for a larger battery-and-solar job on a tight network is often: quote the system the customer wants, apply under G99 with an export limitation scheme that caps grid export at a level the feeder can take, and connect on that basis - rather than downsize the system or wait out reinforcement.

The condition that comes with it

Export limitation is not a form you file and forget. It carries an ongoing commitment, and that is where the compliance risk sits.

Once the scheme is installed and commissioned, the export limit settings are locked. They cannot be altered by the customer, and they can only be changed with the written agreement of the DNO. In practice the settings are protected - by password, PIN or a physical seal - so that the agreed limit stays the agreed limit for the life of the connection. If a later change to the site would lift export above the capped figure, that is a new conversation with the network, not a quiet tweak on site.

For the installer, three things have to be right and stay right:

• The scheme specified in the application matches the equipment actually installed
• The commissioning notification confirms the site is running to the agreed limit
• The settings are sealed and documented, so a future engineer or the DNO can see what was agreed

Get the specification and the installed reality out of step - a different inverter, a firmware change, a battery added later - and you have a connection that no longer matches its agreement.

Where it breaks down at scale

None of this is difficult for one job. The difficulty is volume. At 30 to 50 installs a month across multiple DNO territories, the export-limit jobs are a subset that need extra tracking, and they are exactly the ones that go quiet after the exciting part is done.

The original G99 application is easy to watch because there is a pending outcome. The commissioning notification - the step that formally tells the DNO the site is installed and running to the agreed export limit - is less time-critical in the moment, gets deprioritised against active jobs, and then surfaces weeks later when something does not line up. An unconfirmed export-limit commissioning is a compliance gap sitting on a live connection.

The fix is not another spreadsheet. It is keeping the DNO workflow - application, export-limit condition, commissioning notification and the supporting certificates - in the same record as the customer, the proposal and the scheduled engineer visit. When the export-limit status is visible every time someone opens the project, your office team does not have to remember to chase it. When it lives in a separate tracker from the job, it falls through the gap.

Export limitation turns a job the network would have refused into one you can deliver. The engineering is well established. What decides whether it stays compliant six months later is whether the commitment you made in the application is still being tracked once the install is done. That is what Payaca's DNO workflow is built around.