G98, G99 or SGI: Which Grid Application Do You Need?
The threshold for a G99 application is 16 A per phase, not 50 kW. The three SGI routes, the 10-working-day assessment, and what to ask before you sign.
G98, G99 or SGI: Which Grid Application Does Your Business Solar Need?
Most commercial solar quotations mention a "DNO application" in a single line and move on. That line hides the decision that most often sets a project's programme, and it is routinely described wrongly. The threshold is not 50 kW. It is 16 A per phase, and everything else follows from it.
The line that decides everything
Two Energy Networks Association documents govern connecting generation to a distribution network in Great Britain. EREC G98 covers fully type tested micro-generators up to and including 16 A per phase connecting in parallel with public low voltage distribution networks. EREC G99 Issue 2, published on 10 March 2025, states that it applies to all power generating modules that are not in the scope of G98, or that would be in scope but are not suitable for type testing, or that are designed to work in island mode.
Sixteen amps per phase translates to roughly 3.68 kW on a single phase and 11.04 kW across three phases. Any commercial array worth installing is above that, which is why the figure of 50 kW sometimes quoted as the G99 trigger has no basis in either document. Fifty kilowatts matters elsewhere — for MCS scope, for Smart Export Guarantee certification and for planning — but not here.
What G98 actually covers
G98 is a notification route, not an application. If every generating unit is fully type tested and both individual and aggregate registered capacities sit at or below 16 A per phase, the installer notifies the network operator and no export limitation scheme is required. In practice that covers a domestic installation and very little else.
The three Small Generation Installation routes
Between G98 and a standard G99 application, G99 sets out three Small Generation Installation procedures. Each is defined by three numbers — the intrinsic design capacity of each unit, the registered capacity of each unit, and the aggregate of registered capacities — plus whether an EREC G100 export limitation scheme is fitted.
| Route | Individual intrinsic design capacity | Individual registered capacity | Aggregate registered capacity | G100 export limitation |
| EREC G98 | not applicable | 16 A or less | 16 A or less | No |
| G99 SGI-1 | 32 A or less | 16 A or less | 16 A or less | No |
| G99 SGI-2 | 32 A or less | 16 A or less | 32 A or less | Limited to 16 A |
| G99 SGI-3 | 32 A or less | 32 A or less | 60 A or less | Limited to 32 A |
The pattern is worth reading twice. An export limitation scheme buys you headroom. With a G100 scheme capping export at 32 A per phase, SGI-3 lets the aggregate registered capacity reach 60 A per phase — considerably more generating plant than G98 would ever allow — without a full standard application. On a site with high daytime self-consumption and little interest in export revenue, that trade is often the right one.
The timescales the standard actually commits to
For SGI-2 and SGI-3, G99 commits the network operator to providing the results of its assessment within 10 working days of receiving the application. The planned commissioning date stated on the form must fall between 10 working days and 3 months from submission, and commissioning must be confirmed no later than 28 days afterwards where tests are not witnessed.
Two caveats carry real commercial weight. First, no generating plant should be installed or commissioned before the operator's assessment is complete and the outcome communicated. Second, if the operator decides further analysis is needed, that confirmation ends the SGI process and the application reverts to the standard route with no committed timescale.
Where further analysis is required, G99 is explicit that installation must not proceed until the operator has established whether the network needs upgrading, and whether such work may be chargeable to the generator.
That last clause is the one to raise in procurement. A quotation that does not say who carries a reinforcement cost is not a fixed price.
Standard G99 and Type A
Above the SGI thresholds you are into a standard application. G99 defines a Type A power generating module as one with a connection point below 110 kV and a registered capacity of 0.8 kW or greater but less than 1 MW, which captures essentially every commercial rooftop project.
For Type A, the generator applies using the operator's own standard application form. The operator then assesses whether distribution network studies are required and whether it needs to witness the commissioning tests. In some cases studies must be completed before a firm quotation can be issued. Any works at the connection site and associated facilitating works have to be finished before the module can be commissioned, and the operator sanctions permanent energisation only after the commissioning tests pass.
What this means when you are buying
The application route is not an administrative footnote. It determines whether your project is a ten-working-day notification or a studies-and-quotation exercise with an open-ended programme, and it is set by electrical design decisions — inverter sizing, phase configuration, whether export is limited — that are made before anyone orders equipment.
Three questions settle it:
- What is the aggregate registered capacity, in amps per phase, of everything that can export?
- Is an EREC G100 export limitation scheme fitted, and at what limit?
- Who submits and tracks the application, and who carries any reinforcement cost the operator identifies?
If battery storage is in scope, note that G99 includes electricity storage within its definition of a power generating module, so a battery capable of exporting counts towards those aggregates. That is a design conversation to have early rather than late, and it is covered on our battery storage page.
Where to go next
Verifying an installer's credentials is a separate exercise from verifying the design, and our guide on how to check an MCS-certified installer walks through the registers. For the connection question itself, our commercial solar installers page sets out the surrounding rules — the capital allowances position, the business rates exclusion to 2035, and the Smart Export Guarantee certification split at 50 kW — with each figure referenced to its primary source.
Sources: ENA Engineering Recommendation G99 Issue 2 (10 March 2025), sections 6.1 to 6.2 and terms and definitions; ENA Engineering Recommendation G98. Figures quoted are from those documents. Confirm current requirements with your distribution network operator before relying on them for a specific project.
