If you're planning to install solar panels, battery storage, or other generation equipment in the UK, you need to know whether your project requires a G98 notification or a full G99 application. This guide is for UK homeowners, installers, and businesses planning to connect solar panels or batteries to the grid. It breaks down the rules, walks through the application process step by step, and explains what happens if you skip it.

Quick answer: do you need a G98 or G99 application?

Here is the simple decision rule. If your total inverter export capability is 3.68 kW or less per phase (that's 16 A at 230 V), your solar system typically falls under G98. A G99 application is required for systems exceeding 3.68 kW per phase in the UK, and you must have DNO pre-approval before installation begins. The G99 process includes a mandatory formal request to connect power generation systems.

The practical difference between g98 and g99 comes down to timing. G98 allows installation before notification within 28 days, a straightforward "install, then notify" process. G99 flips this: you apply first, wait for approval, then install.

Some concrete examples:

• A typical 3.6 kW single-phase rooftop solar system → G98
• A 5 kW+ solar array on single-phase → G99
• A 3.68 kW solar inverter paired with a 5 kW hybrid battery that can export → G99
• Plug-in balcony solar up to around 800 W → G98 microgeneration, simple notify-after

Most domestic solar installations fall under G98 regulations. But as battery storage and larger systems become more common, more homeowners are finding they need to navigate the G99 route.

The rest of this article walks through the full g99 application process, timelines, costs, and common questions.

Understanding G98 and G99: key differences for solar systems

G98 and g99 are UK engineering recommendations published by the Energy Networks Association (ENA). They set the technical standards for connecting distributed generation and storage to the electricity distribution network. Think of them as the rulebook your distribution network operator follows when you want to connect solar panels or batteries to the electricity grid.

What G98 covers:

• Smaller systems with export up to 16 A (3.68 kW) per phase
• G98 covers solar systems up to 16 kW total capacity
• Simple notification process, minimal paperwork
• Typically free to submit for all systems and DNOs

What G99 covers:

• Larger solar systems, bigger batteries, and three phase connections
• G99 covers solar systems over 16 kW capacity and any system exporting above 3.68 kW per phase
• Full application with a more detailed technical assessment
• The G99 process includes a mandatory formal request to connect power generation systems

The G99 application process is more detailed than the simpler G98 notification. It involves more forms, more documentation, higher potential fees, and longer timescales, all of which affect your project timeline.

Both g98 and g99 apply to solar PV, battery storage, small wind turbines, and any other generation equipment capable of exporting to the grid. Your installer will usually determine which route applies, but understanding the difference yourself helps you plan realistically.

Do you need a G99 application for your solar panels or battery?

Use this as a quick checklist. The core capacity rule: if your proposed system can export more than 3.68 kW (16 A) per phase at any point, you need a g99 application and must obtain dno approval before installation.

Systems that usually remain G98:

• Plug-in solar up to 800 W
• A 2 kW–3.6 kW rooftop solar system with no or minimal export
• Small hybrid inverter and battery systems configured to limit export at or below 3.68 kW per phase

Systems that typically require G99:

• 4 kW to 10 kW domestic solar arrays on single-phase
• Most three-phase solar installations above 11.04 kW total
• Large home batteries (e.g. 5 kW–10 kW hybrid systems) that can export electricity to the grid
• Small commercial solar or EV vehicle-to-grid hubs

You must apply for G99 before installing larger systems. The G99 application allows for larger renewable installations, enhancing energy capacity while the G99 framework ensures that larger renewable systems do not compromise local grid stability.

Sometimes g98 and g99 apply on the same property. If you already have a G98 solar install and later add a battery whose combined export exceeds 3.68 kW per phase, you will need a new G99 application.

An export-limitation scheme (known as G100) can cap your system's export to keep it within G98 thresholds, but you still need to inform your DNO. If you are unsure, your installer should calculate the per phase export and confirm whether a g98 application or a g99 application is needed.

The G99 application process step by step

Here is the complete approval process from initial design to final acceptance. G99 requires detailed technical assessment and documentation at every stage.

Step 1 – System design

Your installer sizes the solar system and battery, selects inverters (ideally from the ENA Type Test Register), and decides whether export limitation is needed. This is where the nature of your renewable energy project takes shape.

Step 2 – Gather technical information

G99 applications require inverter specifications and system capacity details. You will need:

• Site address and MPAN (Meter Point Administration Number)
• Single or three-phase supply type
• Inverter make, model, and AC/DC ratings from manufacturers
• Total generation capacity and export capacity in kW
• Protection settings (voltage/frequency trip levels, anti-islanding)
• G100 export limitation scheme details, if used
• Certification and compliance documentation (or compliance verification reports for non-type-tested kit)

Step 3 – Choose the right G99 form

The ENA publishes two forms (and supplementary documents) depending on your system. Form A1-2 covers integrated microgeneration and storage. Non-type-tested equipment requires additional compliance documents (A2-1 through A2-3). Your installer will typically determine which forms apply.

Step 4 – Submit to your DNO

Applications go to your local network operator, either via the ENA Connections Portal or the DNO's own website or email. Only one DNO receives the submission. Attach single-line diagrams, datasheets, type test certificates, and any export limitation documentation.

Step 5 – DNO assessment

The DNO verifies your system against local network capacity, checking voltage rise, thermal limits, and fault levels. This is the more detailed technical assessment stage. They may approve outright, impose an export limit, or quote reinforcement costs. A more detailed assessment may be needed for constrained areas.

Step 6 – Offer, acceptance and installation

You receive a formal connection offer with any fees and conditions. Accept in writing. Your installer then schedules installation and commissioning. Do not connect or energise until the offer is signed and conditions are met.

Step 7 – Post-commissioning paperwork

Submit commissioning test results (Form A3-2) to the DNO within 28 days. Once complete, the DNO issues final acceptance. Only then can you legally export and register for an export tariff such as the Smart Export Guarantee.

G98 vs G99 timelines, costs and the 'fast track' route

Understanding the cost and timing difference between these routes helps you plan your project realistically.

G98 applications are free for all systems and DNOs, and approval for G98 typically takes 10 to 15 working days. G99 applications can take up to 60 working days for approval, and fees vary by DNO and project complexity. If network reinforcement is required, costs climb further.

The fast track G99 route is available for projects using fully type-tested inverters with standard protection schemes and export limitation within set bounds. If testing confirms the equipment meets all ENA requirements, and the local network has clear capacity, a simplified assessment can reduce response times. Fast track still requires a G99 form (often A1-2 and related documents) and does not override the need for DNO sign-off.

Projects that sometimes qualify for fast track include domestic solar and battery solutions up to defined export thresholds and smaller systems in unconstrained network areas.

Factor these timelines into your schedule. If you need your solar installation complete before winter or a business opening, submit your g99 application early.

How and where to submit a G99 application (forms, ENA portal & DNO lookup)

Finding your DNO is the first step. Use the Energy Networks Association's "Who is my network operator?" tool to identify which distribution network operator covers your area. The main UK DNOs include UK Power Networks, Northern Powergrid, Western Power Distribution, SP Energy Networks, SSE Networks, and Electricity North West.

Once you know your DNO, you can submit through the ENA Connections Portal or the DNO's own website. The standard G99 Generator Standard Application Form and supplementary forms (A1-2, A2, A3) are downloadable from the ENA's G98 & G99 guidance page.

To complete and submit, attach:

• Single-line diagrams and site plans
• Inverter datasheets with manufacturer certification
• ENA Type Test certificates (entries from the register)
• Export limitation documentation if applicable

Your installer normally handles this entire application process, but you as the homeowner or business owner are the "generator" named on the forms. Keep copies of all documents and correspondence.

For G98 notifications and small plug-in solar, installers use shorter G98 forms submitted after commissioning within 28 days. G99 must always be lodged and approved before work starts, so assess your timeline and submit early.

What if you don't apply? Non-compliance, retrospective G99 and export limits

Consequences of Non-Compliance

The potential impact extends further:

• Home insurance may be invalidated without DNO compliance
• Selling your home may require proof of DNO approval, and missing documentation can delay or block conveyancing
• The DNO can require disconnection at your cost without approval

Retrospective Applications

Retrospective applications are possible. DNOs may accept a late G98 notification or a retrospective G99 application, but they can impose export limits, demand remedial work, or insist on temporary disconnection while they assess the potential impact on the local network. Where the electricity network cannot safely accept the as-installed export, the DNO might require export limitation devices or inverter setting changes to protect the grid safely.

If you suspect your system lacks proper approval, contact your installer or DNO promptly, gather commissioning paperwork, and demonstrate compliance by regularising the connection.

Summary and next steps for your G99 solar application

The rule is straightforward: if your inverter export is 3.68 kW or less per phase, a G98 notification is intended for your project. Anything above that pushes you into G99, where DNO pre-approval is mandatory before installation.

Plug-in solar up to 800 W and smaller rooftop microgeneration follow the quick G98 notify-after path. Larger rooftop solar or battery-backed systems follow the G99 apply-before route with a detailed assessment of your system's grid impact.

Your next steps:

• Calculate your expected export per phase
• Check your DNO via the lookup tool
• Review the latest ENA G98/G99 guidance documents
• Talk to an MCS-certified installer who can manage the full application process

Start your dno approval process early to avoid delaying your installation, especially where G99 and possible network reinforcement are involved. Understanding g98 and g99 from the outset helps you design the right solar system, avoid compliance issues, and maximise export income while keeping the grid safe and stable.