G98 vs G99 — when does V2L trigger DNO notification?
ENA G98/G99 govern equipment that runs in parallel with the public grid. A true islanded V2L feed — physically separated by a changeover so it can never run in parallel or export — is generally outside G98/G99 and is treated as a load. The moment a system can export or synchronise (true V2G/V2H), it is in scope: G98 is the lighter notify-not-approve route for small type-tested microgenerators within the G98 scope threshold, G99 covers larger or island-capable systems and generally needs DNO acceptance before energising. The exact G98/G99 clause locators are Not confirmed pending the official PDFs.
In short
- G98/G99 apply to equipment running in parallel with the grid; true islanded V2L (changeover, no export) is generally outside them, treated as a load.
- G98 = notify-not-approve for small, type-tested microgenerators within the G98 scope threshold, in parallel.
- G99 = larger or island-capable; generally needs DNO acceptance before energising.
- G99 Issue 2 brings electricity storage incl. V2G EVs into scope — new mandatory storage requirements from 1 March 2026.
- Exact G98/G99 clause/section locators are Not confirmed (pending the official PDFs); whether a changeover truly prevents parallel operation is a design-and-test matter.
Where this stops: This explains when the DNO regime applies. Whether a given changeover genuinely prevents parallel operation, and the connection application itself, are competent-person and DNO matters.
Some details below depend on sources still being verified against the published standard, so we mark them Not confirmed rather than guess:
- Exact ENA G98/G99 Issue 2 clause/section locators — the official PDFs are not yet linked in our library, so precise section numbers are inference, not fact. The citation/edition is checked (public-primary); the clause substance is pending a licensed/source-text check, and we render exact locators Not confirmed.
The trigger is parallel operation
G98 and G99 govern equipment that operates in parallel with — synchronised to — the public network. A pure islanded V2L feed, physically separated by a changeover so there is no possibility of back-feed, is generally not a parallel connection. The card's clearest hook: where an EV/charger cannot operate as a V2G EV (cannot export or parallel), it is treated as a load, outside G99.
What the diagram shows: Two arrangements. On the left, the grid and the EV/source are connected together (in parallel) — this engages ENA Engineering Recommendations G98/G99, so the DNO must be notified. On the right, a break-before-make changeover switch connects the load to either the grid OR the EV/source, never both together (islanded) — a source that can never run in parallel or export is generally treated as a load and sits outside G98/G99. Whether a given changeover genuinely prevents parallel operation is a design-and-test matter for the competent person and the DNO. The exact G98/G99 clause locators are Not confirmed pending the official PDFs. Legend (stated in words, not colour alone): L = line/live conductor; N = neutral; E/CPC = earth / circuit protective conductor.
G98 vs G99
- G98 — the simplified, notify-not-approve route for small, fully type-tested microgenerators within the G98 scope threshold, in parallel with the LV network.
- G99 — everything larger, not type-tested, or designed to work in island mode; generally a connection application accepted by the DNO before energising.
- G100 — export/import limitation schemes that cap net flow, which can keep a system in a lower tier. Not usually relevant to island-only V2L.
G99 Issue 2 expressly brings electricity storage, including V2G EVs, into scope, with new mandatory storage requirements recorded as in force from 1 March 2026 — relevant when timing any grid-parallel V2H/V2G advice.
The exact G98/G99 Issue 2 clause/section numbers are not yet confirmed against the official ENA PDFs; the citation/edition is checked (public-primary) while the clause substance is pending a licensed/source-text check, so we render precise locators Not confirmed. Whether a given changeover genuinely prevents parallel operation (a momentary parallel transfer can pull it back into scope) is a design-and-test matter for the competent person and the DNO.
How this is made and proven compliant
- ENA EREC G98 / G99 (parallel connection of generation/storage) + G100 (export/import limitation)
- BS 7671 §551.7 (parallel operation) for the installation side
A competent person determines whether the arrangement is grid-parallel or genuinely islanded, and makes any G99 connection application; the DNO accepts the connection where required.
- Establish whether the system can export/parallel (in scope) or only island via a break-before-make changeover (out of scope)
- For grid-parallel: a G98 notification or a G99 connection application accepted by the DNO before energising
- Prove the changeover genuinely prevents parallel operation (design and test)
Confidence: Inference rolled up across the clauses cited above (the strictest state wins).
Frequently asked questions
Do I need to tell the DNO about a V2L backup?
Generally not, if it is a true island that can never export or run in parallel (separated by a break-before-make changeover) — it is treated as a load. The moment it can export or synchronise (V2G/V2H), G98 or G99 applies and you must notify or apply to the DNO.
What's the difference between G98 and G99?
G98 is a lighter notify-not-approve route for small type-tested microgenerators within the G98 scope threshold. G99 covers larger or island-capable systems and generally needs DNO acceptance before energising.
Why don't you quote the exact G99 section numbers?
The official G98/G99 Issue 2 PDFs are not yet in our reference library, so we treat exact section numbers as inference and render them Not confirmed rather than cite numbers we have not verified.
- Last reviewed
- 14 June 2026
- Written against
- BS 7671:2018 + A4:2026
- Reviewed by
- Martin (qualified UK electrician)
- Next review due
- 14 December 2026
General information, not project-specific design advice. Standards are cited by reference only and never reproduced. How we source this.
References & sources (2)
- ENA — connecting generation/storage to the networks — exact G98/G99 locators Not confirmed pending the official PDFs
- ENA G98/G99 forms