Solar Grid Connection: G98 vs G99 Explained
G98 is the “notify after install” pathway for small-scale generation up to 16A per phase — that’s 3.68kW on a single-phase supply, or around 11kW on three-phase. G99 is the “approve before install” pathway for anything above that. Both are Energy Networks Association engineering recommendations that govern how UK solar PV and battery installs connect to the grid. Most domestic installs are G98. Most commercial installs are G99. Spectrum handles either as part of the standard install scope — you don’t fill in any forms.
G98 and G99 are the two engineering pathways the UK uses to manage embedded generation (solar, wind, battery) connecting to the distribution network. The Energy Networks Association sets the rules. Every UK DNO (National Grid Electricity Distribution, Northern Powergrid, etc.) implements them. The difference between the two is the size threshold and whether you need approval before installing or just notify afterwards.
The size threshold
| Process | Threshold | Equivalent kW | Action timing |
|---|---|---|---|
| G98 | Up to 16A per phase | Up to ~3.68kW single phase / ~11kW three phase | Notify within 28 days after install |
| G99 | Above 16A per phase | Above ~3.68kW single phase / ~11kW three phase | Approval required BEFORE install |
How the export limit affects which one applies
The 16A/phase threshold is on inverter export, not on panel nameplate. A 5kWp panel array with an inverter export-limited to 3.68kW (single phase) sits inside G98. The same 5kWp array with an inverter exporting freely up to 5kW falls under G99.
This is why some domestic installers cap inverter export at 3.68kW — it keeps the install inside the simpler G98 pathway. The trade-off is you can’t export more than 3.68kW even when solar is generating 5kW. For most UK homes with batteries this isn’t a constraint because the battery absorbs the surplus rather than letting it export.
What goes into a G98 notification
G98 is lightweight. The installer submits:
- Site address and MPAN
- Inverter make and model (must be on the certified G98 list)
- Export capacity (kW)
- MCS certificate number
- Commissioning date
Submission is via the DNO’s online portal. The DNO acknowledges within a few days. No engineering review, no approval delay, no risk of refusal.
What goes into a G99 application
G99 is much more thorough. The application includes a full system design, single-line diagram, inverter protection settings, earthing arrangement, photos of the existing meter setup, and battery specification if fitted. The DNO’s statutory window to respond is up to 45 working days (with a 20-working-day Fast Track for smaller, straightforward systems). The DNO can request modifications, refuse outright if local capacity is insufficient, or attach conditions. See our G99 application article for the full process.
Three-phase vs single-phase
Three-phase supplies allow far more headroom under G98 (16A × 3 = 48A total, ~11kW). Single-phase supplies cap at 3.68kW under G98. For homes wanting solar between 4–11kW:
- If single-phase: Choose either G99 (more capacity, longer approval timeline) or G98 with export-limiting (faster but capped output)
- If three-phase: Stay in G98 up to ~11kW combined panel/battery export
Most UK domestic supplies are single-phase. Three-phase is common in larger detached homes, properties with heavy electrical demand (heat pumps + EVs), and most commercial premises. Upgrading from single to three-phase is possible but typically £2,000–£5,000 of work depending on local network conditions.
Not sure which path applies to your install?
Site survey confirms your supply type, allowable export limit and which pathway you fall under. Spectrum handles the full G98 or G99 process as part of the install.
Request a QuoteWhy the distinction matters in practice
- Timeline. G98 commissions and notifies on the same day. G99 needs up to 45 working days for approval. Project timing differs materially.
- Refusal risk. G98 can’t be refused (DNO might query something but ultimately accepts). G99 can be refused if local capacity is insufficient.
- Cost. G98 application is free. G99 application is usually free for sub-50kW but larger systems can attract network study costs.
- Equipment certification. Both pathways require inverter to be on the relevant certified list. Solis hybrids are on both G98 and G99 certified lists.
Battery storage and G98/G99
Batteries on their own don’t generate to the grid — they cycle locally. So battery-only installs (no solar) generally don’t need G98/G99. Where batteries do impact:
- If the battery can export to grid (most hybrid setups can, at least theoretically), its export capability counts toward the 16A threshold.
- If the battery is sized to act as ‘grid services’ (V2G, demand response), it falls under more specific connection processes.
- Most domestic battery installs alongside solar inherit the same G98 or G99 pathway as the solar.
The DNO operators in 2026
UK DNOs by region:
- National Grid Electricity Distribution (formerly Western Power Distribution) — West Midlands, East Midlands, South Wales, South West
- Northern Powergrid — Yorkshire, North East
- Scottish Power Energy Networks — Central and Southern Scotland, Merseyside, North Wales
- SSEN (Scottish and Southern Electricity Networks) — North Scotland, South Central England
- UK Power Networks — London, South East, East
- Electricity North West — North West
For East Midlands solar customers, the relevant DNO is almost always National Grid Electricity Distribution.
FAQs
Do I need G99 approval for a 4kW solar system?
For single-phase supply, yes — unless the inverter is export-limited to 3.68kW (16A × 230V). For three-phase supply, 4kW falls well within G98 territory. Most domestic 4kW installs run export-limited to stay G98 for faster commissioning.
Can I install solar before G99 is approved?
No — for G99 installs, approval must be in place before commissioning. Installing without approval is a regulatory breach and risks disconnection. The installer (Spectrum) takes responsibility for ensuring the right pathway is followed before energising the system.
Does my DNO charge for G98 notification?
No — G98 notification is free. The DNO acknowledges the install for their records. Sometimes a meter operator visit is needed to enable bi-directional metering for SEG, which is also typically free.
What if my G99 application takes longer than expected?
The DNO’s statutory window is up to 45 working days (a 20-working-day Fast Track applies to smaller, straightforward systems), but larger or more complex systems can run 60–90 working days. The DNO usually communicates any delays. Spectrum tracks the application status and updates customers on progress. Install dates are scheduled after approval is in hand.
Who pays the DNO if network reinforcement is needed?
Network reinforcement costs are usually the customer’s responsibility. The DNO costs the reinforcement (cable upgrade, transformer change, etc.) and the customer accepts or modifies the install size. For domestic, reinforcement charges are rare. For commercial, they’re a known consideration on larger installs.
Does adding a battery require G98 or G99?
Battery-only installs typically don’t require G98/G99 because they don’t generate to the grid. Battery alongside solar inherits the pathway determined by the solar’s export capacity. The DNO is most interested in what flows back to the grid, not what cycles locally.
Can I do my own G98 or G99 application?
Technically you can but it requires understanding inverter protection settings, single-line diagrams and engineering recommendations. In practice, an MCS-certified installer handles the application as part of the install. Spectrum’s standard scope includes the full G98/G99 process at no separate cost.
Related reading
- G99 application solar: how DNO approval works
- Why your DNO refused your solar application
- Solar panel installation cost UK 2026
- Solar panel finance UK
For the full Spectrum service overview see contact our team.
Speak to Spectrum Energy Systems
MCS NIC200223. G98 notifications and G99 applications across National Grid Electricity Distribution and Northern Powergrid. Standalone £500 refundable DNO service for commercial prospects.
Speak to Our Team