Before your solar panels can legally export electricity to the grid, your Distribution Network Operator (DNO) needs to know about them. This is not optional – it is a legal requirement. The good news is that for most residential installations, the process is straightforward and handled entirely by your installer.
The DNO application ensures the local electricity network can safely handle your system export. In areas with lots of solar already installed, the grid may have constraints that affect what you can connect or how much you can export. Understanding this process helps you know what to expect and avoid surprises.
This guide explains what DNO applications involve in practice, how to work out which type applies to your system (including with batteries), what can go wrong, and what to ask your installer to ensure the process goes smoothly.
DNO Applications at a Glance
| What it is | Notification/application to connect generation to the grid |
| Why required | Legal requirement; ensures grid safety and stability |
| Who applies | Your installer (on your behalf) |
| G98 (small systems) | Notification only; no approval needed before install |
| G99 (larger systems) | Full application; approval required before install |
| Cost | Usually free; included in installation |
| Timeline (G98) | Notification within 28 days of commissioning |
| Timeline (G99) | Apply before install; 45-90+ working days |
For the broader regulatory context – what DNOs actually do, what they assess during a G99 application, and the escalation routes if things go wrong – see our companion DNO approval process guide. This article focuses on the practical application side: working out which type applies to your system and getting the paperwork right.
What Is a DNO?
Distribution Network Operators
| What they do | Own and operate local electricity distribution networks |
| Their network | Cables, substations, transformers in your area |
| Not the same as | Your energy supplier (who you pay bills to) |
| Responsibility | Getting electricity from transmission grid to your home |
UK DNOs by Region
| DNO | Areas Covered |
|---|---|
| UK Power Networks (UKPN) | London, South East, East of England |
| Western Power Distribution (National Grid) | Midlands, South West, Wales |
| Electricity North West | North West England |
| Northern Powergrid | North East England, Yorkshire |
| Scottish Power Energy Networks | Central/Southern Scotland, North Wales, Merseyside |
| Scottish and Southern Electricity Networks (SSEN) | Northern Scotland, Central Southern England |
G98 and G99 are Engineering Recommendations from the Energy Networks Association’s generation connection guidance – the industry standards each DNO works to. The forms themselves are standardised across all six DNOs, but each operator runs its own portal and has its own processing quirks.
G98 vs G99: Which Applies to You?
G98 – Small-Scale Generation
| Applies to | Most residential solar installations |
| Single phase limit | Up to 3.68 kW inverter capacity per MPPT |
| Three phase limit | Up to 11.04 kW (3.68 kW per phase) |
| Process | Notification only – no pre-approval needed |
| Timing | Notify DNO within 28 days of commissioning |
G99 – Larger Generation
| Applies to | Systems exceeding G98 limits |
| Threshold | Above 3.68 kW single phase / 11.04 kW three phase |
| Process | Full application required before installation |
| Approval required | Yes – cannot install until approved |
| Timeline | 45-90+ working days |
Quick Reference: Which Do I Need?
| System Size | Supply Type | Application Type |
|---|---|---|
| Up to 3.68 kW inverter | Single phase | G98 notification |
| Up to 11.04 kW inverter | Three phase | G98 notification |
| 3.69-50 kW inverter | Single phase | G99 application |
| 11.05-50 kW inverter | Three phase | G99 application |
| Above 50 kW | Any | G99 full application |
The G98 Notification Process
What Happens
| Step | Who | What |
|---|---|---|
| 1 | Installer | Installs and commissions system |
| 2 | Installer | Completes G98 notification form |
| 3 | Installer | Submits to DNO within 28 days |
| 4 | DNO | Acknowledges and records installation |
G98 Notification Information
| Information Required | Details |
|---|---|
| Customer details | Name, address, MPAN (meter number) |
| System details | Inverter make, model, capacity |
| Panel details | Total capacity, number of panels |
| Commissioning date | When system was activated |
| Installer details | Company, MCS certification number |
G98 Timeline
| Event | Timing |
|---|---|
| Installation | Can proceed without waiting |
| Commissioning | System activated |
| Notification deadline | Within 28 days of commissioning |
| DNO acknowledgement | Usually within a few weeks |
The G99 Application Process
G99 Application Steps
| Step | Who | What | Timeline |
|---|---|---|---|
| 1 | Installer | Complete G99 application form | Before install |
| 2 | Installer | Submit to DNO with technical details | Day 0 |
| 3 | DNO | Acknowledge receipt | ~5 working days |
| 4 | DNO | Assess application; network studies | Varies |
| 5 | DNO | Issue connection offer | 45-90+ working days |
| 6 | Customer | Accept offer; pay any charges | – |
| 7 | Installer | Install system | After approval |
G99 Timelines
| Application Type | Target Timeline |
|---|---|
| G99 A1/A2 (under 50 kW) | 45 working days |
| G99 B (50 kW – 1 MW) | 65 working days |
| G99 C (above 1 MW) | 90 working days |
| Reality | Often longer; constrained areas much longer |
Grid Constraints and Export Limits
What Are Grid Constraints?
| Definition | Local network cannot accept more generation |
| Cause | High solar uptake; transformer/cable limits |
| Affected areas | Rural areas; affluent suburbs; anywhere with lots of solar |
| Increasing problem | More common as solar deployment grows |
Types of Constraints
| Constraint | Description |
|---|---|
| Voltage rise | Export pushes local voltage too high |
| Thermal limits | Cables/transformers cannot handle more power |
| Reverse power flow | Substation equipment cannot handle export |
| Fault level | Generation increases fault current beyond limits |
What Happens in Constrained Areas
| Outcome | What It Means |
|---|---|
| Zero export limit | System cannot export at all |
| Reduced export limit | Can export less than inverter capacity |
| Timed export | Export limited during peak solar hours |
| Flexible connection | Export curtailed when network constrained |
| Required upgrades | Must pay for network reinforcement |
Export Limiting
| What it is | Inverter limited to export less than capacity |
| How it works | Inverter programmed with export limit |
| Example | 5 kW inverter limited to 3.68 kW export |
| Self-consumption | Can still use full capacity for home use |
| Common solution | Allows larger systems under G98 |
Export limiting has gone from a niche workaround to the most common way to install a 5-6 kW inverter on a typical UK home. For the technical detail on how it actually works at the inverter level, what happens to the surplus, and which inverters do it well, see our export limitation guide.
Zero Export
| What it is | System cannot export any power to grid |
| How it works | Inverter monitors and prevents export |
| Excess power | Curtailed (wasted) or stored in battery |
| When required | Severely constrained networks |
| Impact | No SEG payments; reduced financial benefit |
Batteries and DNO Applications
Do Batteries Need DNO Notification?
| Battery-only system | May need notification if can export |
| Solar + battery | Combined inverter capacity counts |
| AC-coupled battery | Has own inverter; adds to total |
| DC-coupled battery | Shares solar inverter; no additional capacity |
| Hybrid inverter | Single inverter handles both; counts once |
This is the area that catches most homeowners by surprise. Understanding the difference between AC and DC coupling matters more for the DNO application than for any other reason – see our breakdown on AC vs DC coupled batteries for the technical detail.
Examples
| System | Total Capacity | Application Type |
|---|---|---|
| 3.6 kW solar + DC-coupled battery | 3.6 kW (shared inverter) | G98 |
| 3.6 kW solar + 5 kW AC battery | 8.6 kW total | G99 (single phase) |
| 5 kW hybrid inverter | 5 kW | G99 (single phase) |
| 3.68 kW solar + 3.68 kW battery | 7.36 kW | G99 (single phase) |
If you’re retrofitting a battery to existing solar, the same combined-capacity rule applies. A homeowner with a G98-registered 3.68 kW solar system who adds an AC-coupled battery with its own 5 kW inverter has just pushed the combined site capacity to G99 territory and triggered a fresh DNO application.
Common Issues and Solutions
Application Rejected
| Reason | Solution |
|---|---|
| Incomplete application | Provide missing information |
| Technical errors | Correct and resubmit |
| Grid constraints | Accept export limit or wait for upgrade |
| Non-compliant equipment | Use compliant inverter |
Export Limitation Imposed
| Option | Consideration |
|---|---|
| Accept limit | Still worthwhile if mainly self-consuming |
| Add battery | Store what you cannot export |
| Reduce system size | May get full export for smaller system |
| Pay for upgrade | Rarely economical for residential |
What Your Installer Should Handle
Installer Responsibilities
| Task | Installer Role |
|---|---|
| Determine application type | G98 or G99 based on system size |
| Complete forms | Fill in all technical details |
| Submit application | Send to correct DNO |
| Chase progress | Follow up on G99 applications |
| Configure export limits | Program inverter if required |
| Provide documentation | Give you copy of notification/approval |
Questions to Ask Your Installer
| Question | Why It Matters |
|---|---|
| Is this G98 or G99? | Affects timeline and process |
| Are there known constraints in my area? | May affect export capability |
| Will you handle the DNO application? | Should be included |
| When will notification be submitted? | Should be within 28 days |
| Will I get a copy of the notification? | Important for your records |
If you’re checking whether a quote properly includes DNO application work and is otherwise complete and competitive, our solar panel quote checker walks through the line items a compliant quote should always show.
Costs
G98 Costs
| DNO notification fee | Free |
| Installer admin | Included in installation cost |
| Total cost to you | £0 (included) |
G99 Costs
| Cost Type | Typical Amount |
|---|---|
| Application fee | Often free for small G99 |
| Connection fee | Variable; depends on work needed |
| Network reinforcement | Can be substantial if required |
| Installer admin | May charge extra for G99 handling |
Future System Changes
When You’ll Need Another Application
| Change | DNO Implication |
|---|---|
| Add panels (same inverter) | Notify DNO; usually no fresh application |
| Add panels (more inverter capacity) | Fresh G98 or G99 depending on new total |
| Add AC-coupled battery | Likely G99; combined capacity rule |
| Replace inverter (same size) | Notification; DNO needs updated equipment data |
| Replace inverter (larger size) | Fresh application if it crosses 3.68 kW |
If you’re considering adding more panels to your existing system later, plan the inverter capacity now. An installer can spec a 5 kW inverter on day one with export limited to 3.68 kW, which gives you headroom to add panels later without triggering a fresh DNO application.
After Approval and SEG
Linking DNO Approval to Export Payments
| Step | What Happens |
|---|---|
| DNO acknowledges | System recorded on grid database |
| MCS certificate issued | Required for SEG eligibility |
| Apply for SEG | With your chosen energy supplier |
| Smart meter installed | Required to measure export |
| Export payments begin | Per-kWh tariff for what you export |
If you’re trying to estimate what your export payments might look like once you’ve signed up to SEG with a supplier, our SEG calculator works through typical UK system sizes and current tariff rates.
Summary
| Aspect | Key Points |
|---|---|
| G98 | Up to 3.68 kW single phase; notification only; no pre-approval |
| G99 | Above G98 limits; full application; approval before install |
| Who handles it | Your installer should do everything |
| Cost | Usually free and included |
| Timeline (G98) | Notify within 28 days; no wait |
| Timeline (G99) | 45-90+ working days; wait for approval |
| Grid constraints | May limit export; increasingly common |
| Keep documentation | Important for SEG registration and records |
For most UK residential solar installations, the DNO process is invisible – your installer handles everything, and you do not need to wait for approval. As long as your system stays within G98 limits (3.68 kW inverter on single phase), it is a simple notification submitted after installation.
If you are planning a larger system, battery storage with significant inverter capacity, or live in an area with grid constraints, the process becomes more complex. G99 applications take time and may result in export limitations. Understanding this upfront helps you plan realistically and avoid disappointment.
The key takeaway: make sure your installer includes DNO notification in their service, get a copy of the submitted notification for your records, and ask about any known grid constraints in your area before committing to a system size. If you are told there are constraints, discuss how this affects your options – a battery may make sense if export is limited.
Three things to nail down before you sign. First, get the application type in writing – your quote should explicitly say “G98 notification” or “G99 application”, and if it’s G99, the timeline impact on your install date should be acknowledged. Second, ask about constraints by postcode – any installer worth using in your area will have experience of recent jobs nearby and will know if the local feeder is full. Third, plan inverter capacity around future plans – if there’s any chance you’ll add a battery or more panels later, oversizing the inverter now (with export limiting) saves you a fresh G99 application down the line.
Once you’re up and running, keep three documents safe: the DNO acknowledgement or connection offer, the MCS certificate, and the commissioning paperwork. You’ll need all three when applying for SEG payments and when selling the property.
