G99 application: G98 vs G99, timescales, costs and export limits

G99 and G98: key facts

What is a G99 application?

G99 and G98 are Energy Networks Association engineering recommendations: the technical rules for connecting generators, including solar inverters and batteries, to the distribution network in Great Britain. Your DNO uses them to make sure a new system won't overload cables and transformers, upset voltage, or keep feeding a fault when the grid goes down.

A G99 application is the request to the DNO to connect a system that's too big for G98. In National Grid Electricity Distribution's words, G99 applies to generation and energy storage installations rated above 16A (3.68kW) per phase, or that don't meet G98. The DNO assesses the impact on its network and either confirms you can go ahead or issues a connection offer, which may come with conditions such as an export limit or a price for network works.

G98 vs G99: the 16A per phase line

When a small system still needs approval first

SSEN's G98 guidance says you must apply before connecting, even for a small system, if:

• there's more than one generator at a single property (existing panels count);
• the same installer has fitted generation at another property in the same postcode area in the previous 28 days; or
• total generation at the site goes over the G98 limits.

Thinking about a small balcony-style kit at home instead? See plug-in solar panels.

Who submits the G99 application and the G99 forms

Your installer does. SSEN's guidance is typical: "your installer should submit the application form on your behalf". The forms are the Energy Networks Association's standard G99 forms, published on the ENA website, and your DNO tells you which to use. As an example, NGED splits them like this:

Expect your installer to ask for a location plan, a site layout plan, the manufacturer's specification sheets for the inverters and batteries, and details of your existing supply (your MPAN and the capacity of the incoming supply).

Installer? Businesses reading this page ask us for solar quotes, and we pass each enquiry to one installer only. See how installers receive enquiries from us.

G99 timescales and connection offers

How long a G99 application takes depends on the size of the system, the voltage it connects at, and how busy the local network is. There isn't one number. What the process looks like:

1. Design and application. The installer sizes the system and submits the G99 form with the plans and equipment data.
2. DNO assessment. The DNO studies the impact on its network. For larger schemes it may also need to check the impact on the transmission network.
3. Connection offer. For small type-tested systems the DNO confirms you can proceed. For larger ones it issues a formal offer with any conditions (such as export limits) and a price for any works.
4. Acceptance and works. You accept the offer and pay for any DNO works before they go ahead.
5. Install and commission. The installer commissions the system and sends the commissioning forms. The DNO may witness the protection tests.

The fast routes for smaller systems

• SSEN G99 Fast Track covers smaller low-voltage systems up to 32A. SSEN says it aims to respond within 10 working days. You can't connect until it confirms the assessment is complete; the installer then has up to 3 months to install and commission, and must send Form A3-2 within 28 days of commissioning.
• Northern Ireland: NIE Networks widened G99/NI Fast Track to installations up to 60A per phase from 1 May 2026, with export still limited to 16A per phase.

G99 costs: application fees, connection charges and reinforcement

There are three kinds of cost to ask about:

For a typical rooftop system on a site with a decent supply, the G99 process is mainly a time cost. Where the DNO wants network works, the price can change the economics of the whole project. That's when export limitation earns its keep.

G100 export limitation: fit more solar than the grid will take

EREC G100 is the ENA's standard for customer export limitation schemes. A G100 scheme measures the power flowing at your supply point and throttles the inverters (or charges a battery) so that export never exceeds an agreed figure. It's how a DNO can say yes to a system it couldn't accept at full export.

• In small systems: SSEN's Fast Track categories include systems where a G100 scheme limits export to 16A (3.68kW) or 32A (7.36kW), letting a larger inverter or battery connect on the fast route.
• In commercial systems: the DNO writes any export limit into the connection offer. The installer fits a G100-compliant scheme and submits G100 Form C with the commissioning documents.
• Selling your export: SP Electricity North West notes that exports over 30kW need an export MPAN. The Smart Export Guarantee pays for solar you export, on systems up to 5MW in Great Britain. Suppliers set their own rates; the law only says the rate must be above zero, so shop around.

For a business that uses most of its power in daylight, a zero or low export limit often costs very little, because the panels are sized to the building's own demand. For a warehouse or barn that's empty all day, it matters more, and a battery may be the answer.

Batteries and G99

G99 covers energy storage as well as generation, so batteries count towards the 16A per phase limit. A battery added to an existing solar system, or a hybrid inverter that can discharge alongside the panels, can take a G98 site into G99.

Batteries also help get a G99 application through. A battery controlled as part of a G100 scheme can soak up the solar the DNO won't let you export, and discharge it on site later in the day. That can rescue the design when the DNO offers a tight export limit. See commercial battery storage, or for homes, home battery storage.

Why G99 matters for commercial solar sizing

The grid connection is one of the first things a commercial solar design has to settle, because it decides how much you can export and how fast you can connect:

• Size to your own use first. Every kWh you use on site is worth your import tariff. Exported power earns only the export rate, and it's the export that the DNO limits.
• The 50kW markers. NGED's simplified form covers fully type-tested systems up to 50kW three-phase. SP Electricity North West's commissioning review fee applies above 50kW. Just over a threshold may cost more in process than it gains in output.
• The supply itself. Single-phase sites are capped at 17kW for NGED's simpler form. A three-phase supply makes larger systems easier to connect.
• Export-limited designs. If the DNO caps export, the installer can still fit a larger array and limit what leaves the site, or add a battery.

The cost side: DESNZ's official data puts 10-50kW solar at a median £1,262/kW installed (2025/26). Illustratively, that's about £37,900 for 30kW and £63,100 for 50kW. DESNZ measures cost per kW of declared net capacity (DNC). Installers usually quote per kWp of panels, and DESNZ says costs on that basis (total installed capacity) are typically 6-12% lower: the 10-50kW median is £1,204/kWp. See business solar panel costs and commercial solar panels; for homes, solar panel costs.

What to ask installers about the grid

• G98 or G99, and which form? Have you made G99 applications to our DNO before?
• When will you submit it, and what happens to the design if export is limited?
• Do you expect any DNO connection charges, and who pays any application or witness fees?
• Is a G100 export limitation scheme in the design, and which equipment controls it?
• Does our supply need upgrading, and who arranges it?

We pass your enquiry to one suitable installer that does commercial solar and handles the DNO application.