ENA Engineering Recommendation G98 (ER G98)
Page type: primary-anchored (mirrors ENA EREC G98)
Last updated: 10 April 2026
G98 is the technical standard every domestic solar PV, battery storage, micro-CHP, or small wind installer must comply with when connecting to the GB public low-voltage electricity network. It covers generators up to 16 A per phase (3.68 kW on a standard single-phase household supply). Above that threshold, the larger G99 standard applies.
Source file: ~/knowledge/sources/energy-networks/ena-er-g98.md
Current version: Issue 2, 10 March 2025 (84 pages)
Direct PDF: https://dcode.org.uk/assets/250307ena-erec-g98-issue-2-(2025).pdf
What G98 does, in plain language
When a household or small business installs solar panels or a battery, they are in effect connecting a small power station to the grid. The local Distribution Network Operator (DNO) needs to know about it, and the equipment needs to behave safely.
G98 defines:
- The threshold: 16 A per phase (3.68 kW single-phase, 11.04 kW three-phase). Anything larger goes through the more demanding G99 process.
- Type testing: Manufacturers test a representative design once and register it on the ENA Type Test Register. Every unit from that certified family can then be installed without further testing. Installers do not test individual units.
- What the equipment must do: Stay connected within safe frequency bands, disconnect if the grid loses power to avoid feeding an isolated network section (Loss of Mains protection), limit power output at high frequency (LFSM-O), and meet cyber security baseline requirements.
- What installers must do: Notify the DNO before or within 28 days of commissioning. Complete Forms A, B, and (for decommissioning) D.
- Storage and V2G: From September 2022, electricity storage devices are fully in scope. Vehicle-to-grid (V2G) electric vehicles are included when exporting. New falling-frequency response requirements for storage apply from 1 March 2026.
Key numbers
| Parameter | Value |
|---|---|
| Maximum Registered Capacity (G98 scope) | 16 A per phase |
| Single-phase kW equivalent | 3.68 kW |
| Three-phase kW equivalent | 11.04 kW |
| Sub-800W plant | Reduced requirements (Appendix 1) |
| DNO notification window | Before commissioning or within 28 days |
| Storage: Issue 1 Amdt 5 compliance date | 01 September 2022 |
| Storage: falling frequency requirements date | 01 March 2026 |
Legal framework
G98 compliance is a legal requirement, not just a best-practice standard. The DNO is legally obliged under Electricity Safety, Quality and Continuity Regulations 2002 (ESQCR) Reg 22(2)(c) to refuse connection to non-compliant equipment. The DNO can also require disconnection under ESQCR Reg 26 if a connected unit is causing danger or supply quality problems.
G98 was written to implement the EU Network Code on Requirements for Grid Connection of Generators (RfG, Commission Regulation 2016/631) - specifically the Type A requirements for the smallest generators. Post-Brexit, RfG is Assimilated Law in GB, but G98 itself has not changed; it references GB-specific requirements directly.
Connection process
- Installer selects a Fully Type Tested product from the ENA Type Test Register
- Customer or installer submits Form A (application) to the DNO before starting work
- Equipment is installed and commissioned
- Installer completes Form B (installation document) and notifies DNO within 28 days
- DNO records the connection
For programmes of multiple installations in a Close Geographic Region (same LV feeder, or within 500m of each other, or same postcode sector), a streamlined multi-premises procedure applies.
How G98 fits into the wider rulebook
G98 sits beneath the Distribution Code (DCode), which lists it in Annex 1 as a mandatory implementation standard. The hierarchy runs:
Electricity Act 1989
ESQCR 2002 (Reg 22: connection obligations)
Distribution Code (DCode) - DPC3: generation connections
EREC G98 (up to 16A/phase) / EREC G99 (above 16A/phase)
EN 50549-1 (European standard, incorporated by reference)
Related instruments: - EREC G99: The larger-generator equivalent (Type B/C/D). Installers of rooftop arrays over 16A/phase, or large battery systems, use G99 instead. - EREC G100: Export limitation schemes. Used alongside G98 where a customer wants to cap their export. - Distribution Code (DCode): The parent code. G98 is listed in DCode Annex 1. - RfG Regulation 2016/631: The EU source regulation. G98 implements RfG Type A requirements for GB.
Why this matters for GB energy policy
G98 is the gateway standard for distributed generation at household scale. With roughly 1.5 million domestic solar PV installations in GB and rapid growth in battery storage and V2G, G98 governs the technical behaviour of a material and growing share of GB generation capacity. Issues such as:
- Frequency excursions causing mass disconnection of solar PV (Loss of Mains protection settings)
- Battery storage export behaviour during system stress events
- V2G vehicles acting as grid-balancing resources
...all flow through G98's technical requirements. The RoCoF and LFSM-O settings in G98 are set in coordination with NESO's system operability requirements.
The DCRP modification DC0079 (2018) is a notable precedent: Ofgem directed changes to protection settings across all Type A generators to address system stability concerns, implemented via G98 Amendment 1. This shows how the modification governance chain (Ofgem - DCRP - ENA - G98) can be used to roll out technical changes to millions of distributed assets.