How the G98/G99 thresholds work in amps — converting kW to amps per phase, aggregating across units and lines, and which procedure a system lands on. CLRD routes every job automatically; this guide is for planning — sizing a system to land where you want it.
Every threshold in G98 and G99 is tested against Registered Capacity (RC) — the normal maximum Active Power of a generating unit, declared by the manufacturer and published as a fixed figure on the unit’s ENA Type Test Register entry. It is a property of the device, not the installation: you never enter it, and nothing about your design changes it. The array behind the inverter routes nothing — no DNO form even asks for the panel kWp (it appears on the single-line diagram, and that’s all).
Batteries deserve their own sentence, because two different figures wear the word. A battery-to-grid system — a smart battery with its inverter built in, or a separate battery inverter — counts like any generator, through its inverter’s export rating in kW. Its storage capacity in kWh is recorded on the forms but plays no part in routing, and storage attached to a solar (hybrid) inverter adds no generating unit of its own — the inverter is the unit, and its RC is the cap. A V2G charger routes on its declared export capacity like any storage.
Alongside RC sits Intrinsic Design Capacity (IDC) — the designed maximum. The register doesn’t publish it: check the device’s own display, its datasheet or the manufacturer’s site, and where it is greater than RC — a unit software-limited at the factory to declare a lower RC (settings the installer and customer cannot reach; an installer-set limit doesn’t count) — enter it against the unit in CLRD. Usually the two are equal, and then there is nothing to enter: leave the field blank and IDC is taken as RC. The distinction matters at the first boundary below.
The limits are written in amps per phase, on the 230 V phase-to-neutral basis:
The common slip is using √3 with 230 V. The three-phase formula is kW ÷ (√3 × 0.4) — the 400 V line-to-line basis — which is the same as ÷ 0.69; mixing √3 with 230 V overstates the current by 73% and mis-routes the job.
With the amps in hand, the route follows ENA G99’s own table (all figures per phase; every unit must be Fully Type Tested):
| Procedure | Each unit RC | Aggregate RC | Export limit | DNO approval first? |
|---|---|---|---|---|
| G98 | ≤ 16 A (and IDC ≤ 16 A) | ≤ 16 A | — | No — install, then notify (Form B) |
| G99 SGI-1 | ≤ 16 A (IDC up to 32 A) | ≤ 16 A | — | No — install, then notify (A3-3) |
| G99 SGI-2 | ≤ 16 A | < 32 A | G100 scheme to ≤ 16 A | Yes — apply first (A1-2) |
| G99 SGI-3 | ≤ 32 A | < 60 A | G100 scheme to ≤ 32 A (waived when aggregate ≤ 32 A) | Yes — apply first (A1-2) |
| G99 General Type A | any | < 50 kW three-phase / 17 kW single-phase | if declared | Yes — apply first (A1-1) |
| Type A above 50 kW, and Types B / C / D | any | ≥ 50 kW three-phase / 17 kW single-phase (Type A to 1 MW; B / C / D beyond) | — | Yes — the DNO’s full Standard Application Form. Not supported by CLRD |
Note the IDC gate on the first row: a unit software-limited to 16 A RC but designed for more (IDC 16–32 A) is not G98 — it takes SGI-1, which for the installer is the same install-then-notify process on a different form. And since 2.1 CLRD also checks which standard a unit is type tested to per route — G98 takes G98-tested devices, the SGI procedures take either, a Type A application takes G99 only (see the find-my-device guide).
On timing: the “10 working days” often quoted for these applications is the DNO’s initial response, not the consent. For SGI-2, G99 has the DNO return its assessment within 10 working days; for SGI-3 it commits only to saying, within 10 working days, whether a site-specific study is needed — and where one is, approval waits on it. In practice allow anywhere from two to ten weeks. The same figure bounds the other end too: the planned commissioning date on the application must sit between 10 working days and 3 months out — the window CLRD enforces on the proposed installation date.
| System | Amps | Route |
|---|---|---|
| One 3.68 kW inverter, single phase | 16.0 A | G98 — install, then notify within 28 days |
| One 5 kW inverter, single phase | 21.7 A | SGI-3 — over 16 A so a G99 application, but aggregate ≤ 32 A so no export limitation needed |
| 3.68 kW solar + a 5 kW smart battery (not solar-connected) | 16.0 + 21.7 = 37.7 A | SGI-3 with a G100 scheme limiting export to ≤ 32 A — the aggregate is past the waiver |
| A 3.45 kW software-limited unit (5.5 kW design) | 15.0 A RC, 24 A IDC | SGI-1 — micro-sized RC, but the IDC gate takes it out of G98 |
| Three 3.68 kW inverters on a three-phase supply, one per line | 16.0 A max line | G98 — the aggregate is the busiest line, and the lines balance |
None of this arithmetic is entered anywhere: CLRD reads each unit’s RC, phase and type tests from its frozen ENA register snapshot — plus the IDC you entered, where it differs — totals per line, and routes the job deterministically — the route and its forms appear the moment the job validates, and the evaluation’s trace records every intermediate figure. Use the guide the other way around: to size a quote so the job lands on the procedure — and the timeline — you want.