How to Get Your DNO G98 and G99 Applications Right — First Time

Neil Avery
Oct 30
4 min read

Why Correct DNO G98 and G99 Applications Matter for Solar PV Installers

Connecting solar PV or battery storage systems to the UK grid isn’t just a formality — it’s a compliance process that demands accuracy.

Every week, Grid Guru supports installers who’ve had applications rejected or delayed due to missing data, wrong inverter details, or skipped pre-application steps. In fact, over 30% of our work involves fixing these errors after installations are complete — time that could have been saved with the right process from day one.

This article explains what every installer needs to know about DNO G98 and G99 applications, and how a proper workflow prevents delays, lost income, and unnecessary stress.

Why Correct DNO Applications Matter for Solar PV Installers

Distribution Network Operators (DNOs) oversee the local electricity grid and must approve any generation connected to it. When DNO G98 and G99 Applications are incomplete or inaccurate, they’re either rejected outright or held up for weeks while clarification is requested.

A single mistake — such as the wrong inverter Type Test certificate or missing single-line diagram — can delay your job, prevent MCS certification, and block the system from being energised legally.

At Grid Guru, we’ve seen everything from domestic 3.6 kW hybrid installs to 250 kW commercial arrays rejected for the same simple errors:

Wrong inverter reference number on the ENA database
Missing Letter of Authority
Incorrect schematic format
No pre-application for higher export systems

By handling the paperwork correctly at the start, you eliminate these pitfalls entirely.

The Difference Between G98 and G99 Applications Explained

G98 applies to smaller single-phase systems (typically up to 16 A per phase). These can be installed and then notified within 28 days.

G99 covers any system exceeding that limit — typically commercial or larger domestic projects. These require pre-approval before installation can begin.

Understanding the boundary between G98 and G99 is vital:

Install under G98 when you should have applied under G99, and you risk a formal breach of the Electricity Safety, Quality and Continuity Regulations (ESQCR).

Why Pre-Application Checks Are Essential for G99 Projects

Before installing larger systems, a G99 pre-application gives the DNO a chance to assess grid capacity at the connection point.

They’ll determine if there’s room for your export or if reinforcement work is needed.

Skipping this step can result in:

Export limitations being imposed after installation
Delays to your commissioning
In some cases, refusal to connect

Grid Guru manages this process by preparing a concise pre-application with full site data, inverter details, and export requirements — ensuring the DNO can make a quick, informed decision.

Post-Installation Notifications — The 28-Day Rule You Can’t Ignore

For G98 systems, installers must notify the DNO within 28 days of commissioning.That notification must include:

Site address and MPAN
Commissioning date
Inverter and battery details
Type Test certificates
Test results

Missing or inaccurate data will trigger a rejection. We routinely see notifications bounced back because of incomplete inverter data and site errors.

Our system ensures that every DNO submission includes the right attachments, formatted to the DNO’s preferred specification.

Avoid Rejection: Matching the Correct Inverter Type on the ENA Database

One of the most common (and frustrating) reasons for DNO G98 and G99 Applications rejection is an outdated inverter Type Test certificate.

Every approved inverter has an ENA reference, such as SUNSY/05864/V2/A1.If your application references V1 when the DNO now requires V2, it will be returned — even if the inverter itself hasn’t changed.

We cross-check every product against the live ENA Type Test Register, ensuring full compliance before submission.This one simple check saves days of back-and-forth with the DNO and keeps your commissioning on schedule.

How Grid Guru Helps You Avoid Costly DNO Rejections

When you use Grid Guru for your DNO G98 and G99 Applications, you’re not just outsourcing admin — you’re gaining a technical partner. We verify every aspect of your submission, including:

Site and MPAN verification
Single-line schematics
Export limit confirmation
Pre-application submission (for G99)
Commissioning documentation (for G98/G99)

We liaise directly with the DNO on your behalf, respond to queries, and keep your installation fully compliant through to completion.

The result?

Accurate Submissions.
Faster approvals.
Installers free to focus on what they do best — installing systems, not chasing paperwork.

Save Time and Stay Compliant with Grid Guru’s End-to-End DNO Service

With grid connection rules tightening and networks becoming more congested, DNO Applications demand precision. Whether you’re fitting a 3.6 kW hybrid or a 200 kW rooftop system, the same principle applies: get it right the first time.

Our team handles hundreds of G98 and G99 applications every month — and we’ve refined the process so your jobs never stall.