Every solar installation in South Wales requires notification to the local Distribution Network Operator before the system can be commissioned and connected to the grid. Getting the DNO process right — and managing it proactively — is the single most common source of programme delay on commercial solar projects. This guide explains the G98 and G99 framework, the two DNOs covering South Wales, current approval timelines, and the pre-application checks FLD performs before committing to installation dates.
G98 versus G99: the threshold
The Engineering Recommendation G98 applies to small-scale generation installations below 3.68 kW per phase (16A per phase at 230V). For a single-phase domestic installation up to 3.68 kWp, G98 requires only notification to the DNO within 28 days of commissioning — not prior approval.
The Engineering Recommendation G99 applies to all installations above this threshold. G99 requires prior approval from the DNO before the installation is connected. The G99 framework divides installations into Type A, B and C categories based on installed capacity and connection voltage.
G99 Type A: Single-phase or three-phase installations up to 1 MW connected at low voltage (LV, 400V). The majority of commercial rooftop solar installations fall here.
G99 Type B: Installations above 1 MW connected at LV, or any installation connected at high voltage (HV, 11 kV). Industrial-scale rooftop systems and ground-mounted arrays above 1 MWp.
G99 Type C: Installations requiring dedicated DNO infrastructure upgrades, typically above 5 MW.
The two DNOs in South Wales
South Wales is divided between two Distribution Network Operators:
NGED (National Grid Electricity Distribution) covers:
- Swansea and the Swansea Valley (SA1 to SA9)
- Neath and Port Talbot (SA10 to SA13)
- Cardiff and the Vale of Glamorgan (CF1 to CF72)
- Newport and Gwent (NP1 to NP25)
- Merthyr Tydfil and the Heads of Valleys (CF47 to CF48)
- Bridgend (CF31 to CF36)
SP Manweb covers:
- Carmarthenshire (SA14 to SA33)
- Pembrokeshire (SA61 to SA73)
- Ceredigion (SY23 to SY25)
- Powys (LD, SY, NP8)
The Loughor estuary forms the approximate boundary between NGED and SP Manweb in the Llanelli-Gorseinon area. Properties in SA4 (Gorseinon) are NGED; SA14 and SA15 (Llanelli) are SP Manweb.
Current approval timelines (2026)
G98 notification (all DNOs): 28 days post-commissioning, no prior approval required. FLD submits G98 notifications on the day of commissioning.
G99 Type A — NGED: 10 to 14 weeks from submission to approval for well-prepared applications with no network constraint issues. Applications with export limiting or battery storage management require additional protection relay coordination, adding 2 to 4 weeks.
G99 Type A — SP Manweb: 14 to 20 weeks from submission. SP Manweb has historically run longer approval timelines than NGED due to lower staffing levels relative to the rural network’s complexity. Applications submitted in Q1 (January to March) typically move faster than Q3 (July to September) when the agricultural and rural new-build pipeline creates a seasonal application peak.
G99 Type B — NGED: 20 to 30 weeks. Distribution planning involvement from week 8. Likely to require a protection settings study and site-specific protection relay configuration.
G99 Type B — SP Manweb: 25 to 35 weeks. Rural high-voltage network constraints make Type B assessments more complex in the SP Manweb area, particularly in the Pembrokeshire and Powys catchments.
What causes DNO delays
Incomplete applications: G99 applications require a detailed single-line diagram, generation equipment specification sheets, protection relay settings, and site plan. Incomplete submissions are returned — adding weeks to the programme.
Network export headroom exhaustion: Many South Wales substations are approaching their export capacity limit due to the volume of solar applications submitted in the past 5 years. Applications in constrained areas require export limiting or battery management controls, which must be specified in the application.
Protection relay coordination: G99 Type A installations above 50 kWp require protection relay settings coordinated with the DNO’s protection engineer. This is a sequential process that cannot be parallelised with other project activities.
Voltage rise assessment: In rural areas with long distribution spurs, the DNO’s voltage rise calculation may determine that the solar system requires export limitation to avoid exceeding the statutory voltage band at the point of connection.
FLD’s DNO process
FLD runs a pre-application feasibility check before committing to project programme dates. This includes:
- Identifying the correct DNO for the site postcode
- Submitting a pre-application network enquiry to confirm export headroom at the relevant substation
- Confirming whether export limiting or battery storage is required to secure approval
- Preparing a complete G99 application pack (single-line diagram, equipment schedules, protection relay specification) at the start of the project programme
DNO approval is treated as the long-lead programme item. FLD schedules panel and inverter procurement to complete within the DNO approval window, so that installation can begin immediately on receipt of approval.
For commercial projects where programme certainty is critical, FLD advises clients to allow a minimum 14-week DNO window for NGED and a 20-week window for SP Manweb from project commitment to commissioning.
Call Paul on 01792 680611 to discuss DNO pre-application checks for your site.