What is a DNO Solar Application? A UK Homeowner’s Guide to G98, G99 & Grid Approval
Updated: Aug 4
Planning a solar PV and battery installation for your property requires more than just mounting panels on the roof—it requires official permission from your local Distribution Network Operator (DNO).
Whether your home falls under Northern Powergrid (covering Yorkshire and the North East) or Electricity North West (ENW), every grid-connected solar and battery system in the UK must comply with Energy Networks Association (ENA) grid regulations.
This guide explains what a DNO application is, the key differences between G98 and G99 connection pathways, how export limits work, and how Think Free Solar handles the entire regulatory process on your behalf.
What is a Distribution Network Operator (DNO)?
A DNO is the company responsible for maintaining the physical cables, substations, and towers that deliver electricity from the national grid to your home’s main fuse box.
Unlike your energy supplier (such as Octopus Energy or OVO), who bills you for electricity usage, your DNO manages the underlying infrastructure.
When you generate excess solar power or discharge a battery back to the grid, power flows in reverse through your local substation. The DNO must evaluate your system to ensure local power lines can handle the extra voltage without causing localized blackouts or transformer overloads.
G98 vs G99 Applications: What’s the Difference?
The size of your inverter dictates whether your installation follows the simple G98 notification route or the more detailed G99 pre-approval process.
Important Note: DNO thresholds are calculated strictly on inverter export power (in kW), not on battery storage capacity (in kWh) or raw solar panel wattage. For example, you can pair a 15kWh battery with a 3.68kW inverter and still qualify under G98 rules.
Feature | G98 Application (Micro-generation) | G99 Application (Larger Systems) |
Inverter Threshold | $\le 3.68\text{ kW}$ single-phase / $\le 11.04\text{ kW}$ 3-phase | $> 3.68\text{ kW}$ single-phase / $> 11.04\text{ kW}$ 3-phase |
Process Pathway | "Fit and Notify" | "Apply and Wait for Approval" |
DNO Approval Needed? | No prior approval needed | Yes — approval required before energising |
Timeline | Immediate; notification within 28 days | Fast Track: 10–20 days; Full: 45–65 working days |
Typical Setup | 4kW–6kW panels with 3.68kW hybrid inverter | 8kW+ panels, high-output inverter or 3-phase supply |
Understanding Export Limits & G100 Protection
If you want a large solar array (e.g., 6kW to 10kW) on a standard single-phase UK supply, local grid constraints might restrict how much electricity you can export during peak generation hours.
To prevent grid congestion without capping your household energy production, your installer can fit a G100 export limitation device. This hardware dynamically caps the export to the approved limit (such as 3.68kW) while allowing your home and battery storage to absorb the full 8kW generation capacity.
3-Phase Upgrades & Complex Connections
For larger properties, farm buildings, or homes with multiple EV chargers, heat pumps, and extensive solar arrays, single-phase connections can become a bottleneck.
3-Phase Connection Limit: Moving to a 3-phase supply expands your G98 threshold up to 11.04kW combined output.
Commercial & Rural Installations: Farms and rural Yorkshire properties served by older single-wire earth return (SWER) networks almost always require a formal G99 grid assessment before installation.
The DNO Application Process with Think Free Solar
Navigating DNO technical specifications, single-line wiring diagrams (SLDs), and protection settings can feel overwhelming. At Think Free Solar, our engineering team manages the entire regulatory pathway on your behalf.
What We Handle for You:
MPAN & Fuse Assessment: We inspect your main service head (cut-out fuse) to ensure it can safely handle your new generation equipment.
Schematic Drafting: We create exact single-line electrical diagrams detailing your hybrid inverters, battery storage, and isolation switches.
Direct DNO Negotiation: We liaise directly with Northern Powergrid, ENW, or National Grid engineers to secure the maximum possible export allowance for your property.
Smart Tariff Readiness: Once DNO approval and MCS paperwork are finalized, we provide the documentation needed to register for premium export tariffs like Octopus Outgoing.
Frequently Asked Questions
Can a G99 DNO application be rejected?
Yes. If local high-voltage transformers are congested, a DNO may limit your permitted export or request payment for network upgrades. Using export-limiting devices (G100) or smart battery storage usually resolves capacity issues without costly grid work.
How long does Northern Powergrid take to approve a G99 application?
For standard residential installations qualifying for G99 Fast-Track, approvals used to be issued within 10 to 15 working days. Larger or more complex grid connections can take up to 45 working days. However, current backlogs within Northern Powergrid have resulted in even straightforward applications taking significantly longer.
Thinking of adding solar PV or battery storage to your property? Let Think Free Solar manage your DNO grid application from start to finish.
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