The most common home system sold today is a 5 kW or 6 kW hybrid inverter with a battery. It is over 16 A per phase, so it is not G98. It is also far too small for the full G99 machinery. EREC G99 Issue 2 (March 2025) put three lanes between the two: the Small Generation Installation procedures, SGI-1, SGI-2 and SGI-3.
This is part 2 of DNO applications by size. If you sell hybrids, these three lanes are most of your DNO work, and the difference between them is a setting and a device.
The three lanes in one table
G99 section 6.2.2 sets the conditions in amps per phase. Every SGI lane starts from the same ground: a single installation, every unit fully type tested and on the ENA register, and no unit with an intrinsic design capacity above 32 A (7.36 kW on one phase).
| Lane | Each unit's rating | Each unit set to | Site total per phase | G100 export limit | Before install | After |
|---|---|---|---|---|---|---|
| G98 | 16 A or under | 16 A or under | 16 A or under | none | nothing | G98 Form B |
| SGI-1 | 32 A or under | 16 A or under | 16 A or under | none | nothing | Form A3-3 |
| SGI-2 | 32 A or under | 16 A or under | under 32 A | 16 A | Form A1-2, 10 working days | Form A3-2 |
| SGI-3 | 32 A or under | 32 A or under | under 60 A with a limit, or 32 A or under without | 32 A | Form A1-2, 10 working days | Form A3-2 |
Two capacities appear in that table, and the lanes exist because they differ. The intrinsic design capacity is the unit's rating. The registered capacity is what it is set to. A 5 kW hybrid has an intrinsic capacity of 21.7 A. Set it to 3.68 kW and its registered capacity is 16 A.
SGI-1: set it down, connect and notify
SGI-1 is the lane for a bigger inverter turned down. The units may be rated up to 32 A each, but every one is set to 16 A or under, and the site as a whole stays at or under 16 A per phase.
Meet that and there is no application. Install, commission, and send Form A3-3, the notification for a set-down system. The SGI-1 clause names no deadline for it, so send it at commissioning, as you would a G98 Form B. The form records both figures for each unit: what it could do and what it is set to.
The set-down is a real setting, made on the inverter and declared on the form. It is not a number chosen to clear a gate. Lifting it later is a new application on Form A1-1 or A1-2, because the site no longer meets the SGI-1 conditions. The customer loses the output above 3.68 kW on a bright day, and the quote should say so. For many homes the clipped energy is small; a battery that charges from the clipped output changes the sum, and that is a design question, not a DNO one.
SGI-2: a 16 A export limiter on a bigger site
SGI-2 keeps every unit set to 16 A or under, lets the site total go up to just under 32 A per phase, and adds a device: a fully type tested EREC G100 export limitation scheme that caps what leaves the property at 16 A per phase.
The operator's exposure is the export, so the export is what the scheme controls. The generation behind it can be larger. A solar inverter and a battery inverter on one phase, each at 16 A, with a G100 limiter at 16 A, is the shape of it.
SGI-2 is an application. You send Form A1-2 and the operator assesses it within 10 working days. Nothing is installed or commissioned before the answer. The commissioning date on the form must sit between 10 working days and three months from submission. After commissioning, Form A3-2 confirms it within 28 days.
SGI-3: registered kit up to 32 A
SGI-3 is the lane for a hybrid run at full output. Each unit may be registered at up to 32 A. The site total per phase may go up to just under 60 A provided a G100 scheme limits export to 32 A per phase. If the site total is 32 A or under, the scheme is not required at all.
That last clause is the one most single-hybrid homes use. A 5 kW hybrid on its own is 21.7 A, under 32 A, so SGI-3 applies with no limiter. Two 5 kW hybrids on the same phase are 43.5 A, so a 32 A export limiter is needed, or the job leaves the SGI lanes for Form A1-1.
SGI-3 is also an application on Form A1-2, and the operator has 10 working days. What it confirms in those 10 days is whether it needs to do site-specific analysis. If it does not, you proceed. If it does, no further information is required from you, but installation waits until the operator has established whether the network needs upgrading and on what terms. That is the point where an SGI-3 job can turn into a standard application with an offer.
What Form A1-2 asks for
Form A1-2 is short, and most of it is already in a design.
- The customer, the installation address and the MPAN.
- The installer, with the MCS accreditation.
- The existing generating units, if any.
- The proposed units: manufacturer, the register reference (the Product ID), the energy source and technology codes, the registered capacity per phase at 230 V, and the power factor.
- The export limitation scheme, where one is used: the limit in amps, a single line diagram of the scheme, and a description of how it fails safe.
- Five eligibility confirmations: a single installation, no unit over 32 A, every unit fully type tested, the site under the lane's ceiling, and a G100 scheme where the lane requires one.
- A target date between 10 working days and three months out.
- A signature and a date.
The register reference is the one that trips people. It is the ENA Type Test Register's own identifier for the exact model, not the manufacturer's part number. The same model can carry a compliant and a non-compliant entry for different revisions.
Where these lanes go
Connect Direct takes all three SGI lanes for homes under 17 kW per phase, alongside G98 and the ordinary domestic G99. The platform decides the lane itself after submission, from the register capacities of the devices, the supply's phases and any export limiter you declare. Several operators also run their own fast-track addresses for the SGI lanes on the same 10-working-day clock.
Questions installers ask
Which lane is a single 5 kW hybrid?
At full output on a register-listed unit, SGI-3 without a limiter, because 21.7 A is under 32 A. Set down to 3.68 kW, SGI-1. The first is an application with a 10-working-day wait; the second connects and notifies.
Is a set-down the same as an export limiter?
No. A set-down caps what the inverter produces. An export limiter caps what leaves the property and lets the generation behind it be larger. SGI-1 uses the first; SGI-2 and SGI-3 with a scheme use the second, and the scheme must itself be fully type tested to EREC G100.
Can I use SGI-3 with an inverter that is not on the register?
No. Every SGI lane requires every unit to be fully type tested. An unlisted inverter goes to Form A1-1, in part 3, whatever its size.
Does the battery's rating count towards the 32 A?
Yes. G99 counts electricity storage devices in the aggregate of registered capacities. A hybrid with a DC-coupled battery is one unit at the hybrid's rating. An AC-coupled battery with its own inverter is a second unit.
Solar Engine records the set-down on the design as a declared value, so the band is judged on the set figure while the sizing stays on the rating. The picker names the lane and the form before the quote is sent, and the CRM files the A1-2 or the A3-3 from the same record.