Every band in this series turns on a handful of facts that have nothing to do with the panels. Which operator. Which MPAN. How many phases. What is already generating on the supply. What the inverter is set to. Get those right on the survey and the form is clerical. Get one wrong and the application comes back, or worse, goes through and describes a system that does not exist.
This is part 6 of DNO applications by size, and the last. It is the checklist for the day before you apply, whatever the size.
Which operator
Great Britain has fourteen distribution licence areas run by six groups: UK Power Networks, National Grid Electricity Distribution, SP Energy Networks, SSEN, Northern Powergrid and Electricity North West. The boundaries are not county lines. Weymouth is SSEN, not National Grid; the Wirral is SP Energy Networks, not Electricity North West.
The MPAN settles it. The first two digits of the 13-digit core, the distributor ID, name the licence area: 10 to 23 are the six groups' areas. Read it off the bill or the meter and you have the operator.
A distributor ID of 24 or above is an independent distribution network operator, an IDNO. New estates, retail parks and some commercial sites sit on IDNO networks. The application goes to the IDNO, not to the host operator whose area surrounds it, and the IDNO's own timescales apply.
Which MPAN
The import MPAN identifies the supply the generation connects to. It goes on every form from G98 Form B upwards, and a wrong one sends the application to the wrong operator or the wrong premises. Take it from a bill or the meter, not from memory.
The export MPAN is separate. The operator's registration service creates it, usually at the request of the supplier the customer chooses for export, and some operators raise it from the notification itself; the supplier settles export against it. You do not create it, and the application does not need it unless one already exists. If the customer wants an export tariff, the sequence is: the connection, the export MPAN, then the supplier.
One supply is one case. A site with two supplies, and two MPANs, is two applications, each judged on its own phases and its own aggregate.
Phases and the cut-out
Everything in G98 and G99 is measured per phase. A single-phase supply divides nothing; a three-phase supply divides a three-phase inverter by three and a single-phase inverter by one.
The cut-out is the fact behind two questions. Its rating tells you what the supply is protected to, and Connect Direct asks for a photograph of it with the notification. Its rating is not the estimated maximum demand after installation; that is a separate judgement, and we wrote about the difference in estimated maximum demand and cut-out rating. Photograph it square on, in focus, with the rating legible.
What counts as capacity
The operator adds up the registered capacity of every generating unit on the supply, per phase. The list is longer than the new panels.
- The solar inverter. Its AC rating, not the array's kWp.
- The battery. A hybrid is one unit at the hybrid's rating. An AC-coupled battery is a second unit at its own inverter's rating. Storage without solar is still generation to the operator.
- Existing generation. The array from 2012, the other installer's battery, the standby diesel set. Ask on the survey, read the bill for a feed-in tariff or export line, and look at the aerial photo.
- Single-phase units on a three-phase supply, counted on the phase they sit on. Two single-phase inverters on one phase are added together on that phase.
The sum decides the band. A property can be G98 for the new system alone and G99 for the property, and the operator judges the property.
Rating, setting and limit
Three numbers describe one inverter, and the forms ask for two of them.
- Intrinsic design capacity is the rating.
- Registered capacity is the setting: the rating, or a set-down declared on the form.
- The export limit is an EREC G100 scheme's cap on what leaves the property, which lets the generation behind it be larger.
A set-down moves a 5 kW hybrid from an application to connect-and-notify on SGI-1. An export limiter opens SGI-2 and SGI-3 for bigger sites, and at commercial scale it can turn an offer that permits 150 kW of export into a connection for a 250 kW array. The scheme must itself be fully type tested to G100, and it needs its own drawing and its fail-safe description. Neither is a number chosen to clear a gate; both are settings you make and declare.
Headroom, before you design to a number
Under 50 kW the operator's answer is usually yes, because a small export at low voltage is not bound by the capacity of the primary substation, though a weak feeder can still say no on voltage rise. Above 50 kW it can be no, or yes at a price, and the price comes from the network rather than the roof.
Before you design a commercial site to a number, ask. Every operator publishes a heat map of substation headroom, and every one will give a budget estimate, usually free, on a short description of the scheme. A budget estimate is not an offer, but it tells you whether 200 kW on that roof is a project or a reinforcement bill. The published headroom is a screen, not a promise: a primary with spare capacity can sit under a bulk supply point that has none.
What changes an application
Once an application is in, three kinds of change matter.
- More capacity, or a different inverter. A new application. The operator assessed a specific set of units.
- Less capacity. Recorded on the installation document. No new application.
- A change of phase. A new form, because every number on the old one was per phase.
Answer any request for information on the same reference, in one reply. The operator's clock pauses while it waits, and a thread that splits into three emails is the one that gets lost.
After the connection
Two obligations outlast the install.
The installation document, whichever form it is, goes in within 28 days of commissioning on every apply-first lane, or at commissioning where the operator witnesses the tests. And when a system is removed, the operator is told: within 28 days under G98, and on Form D1 under G99, so the property's registered capacity is corrected and the next installer's application is judged on the truth.
Northern Ireland and Ireland
None of the GB forms apply across the water. Northern Ireland runs G98/NI and G99/NI through NIE Networks, with its own online application and its own forms, and the ENA register marks NI approval separately. The Republic of Ireland's ESB Networks uses its own procedures: a fit-and-inform route for micro-generation and an apply-first route above it, on different capacity lines from G98 and G99.
Questions installers ask
How do I find the operator without a bill?
From the address, by the licence-area boundaries the operators publish, or by asking the customer for the distributor ID on the meter. The MPAN is the only one of those that is exact, and the only one that reveals an IDNO.
Does a battery-only install need a DNO form?
Yes. A battery inverter is a generating unit. Under 16 A per phase and on the register it is G98; above that it is one of the G99 lanes, exactly as solar would be.
The customer already has 4 kW of solar. Is my 3.68 kW system G98?
No. The property is the unit of assessment. 4 kW plus 3.68 kW on one phase is 33 A, so the property is a G99 application, and the existing system goes in the existing units table.
Can I ask the operator before I have a design?
Yes, and for commercial sites you should. A budget estimate needs the address, the MPAN, the phases, the rough capacity and the preferred connection point. It is the cheapest test of a site you will ever run.
Solar Engine reads the operator from the point on the map and the MPAN from the bill, asks for existing generation on the design, counts the battery and the set-down in the band, and opens the headroom request from the same screen the application is filed from.