What is a G99 Application?

Jason Latest Leave a Comment

The District Network Operator (DNO) for each area of the country is responsible for the property’s energy supply and management of it’s export. Sometimes, there are multiple properties in one area that may be exporting power to the grid at the same time. This might result in the DNO for that area restricting the export. This does not affect the PV system, only what might be exported back to the grid.

If a renewable energy system is 3.68kW (per phase) or under, it falls within the G98 recommendation. This is typically known as a ‘connect and notify’ project. Here, the system can be installed and the DNO can be notified within 30 days of the system being commissioned.

If a system is above 3.68kW (per phase), then if falls under the G99 recommendation. This can happen either if the inverter is over 3.68kW, or a combination of smaller inverters totals over 3.68kW. In this case, a ‘grid connection agreement’ needs to be applied for and approved by the DNO prior to any installation work taking place. This can take several weeks for the DNO to process. A G99 application is also required where the battery can provide back up power to the property in the event of a power cut, irrespective of the system size in kW.

It is important to note that the kW values that the DNO are concerned with are the output of the inverters and charge controllers. They are not concerned with the size of the PV array. For example, you could have a 4.0kWp PV array with a 3.68kW PV inverter. In this case the system would fall under G98 because the output of the inverter is 3.68kW or below.

There is a special case if there is a second inverter being installed (or already fitted) as with a battery storage system, and both the PV inverter and battery charge controller are under 3.68kW then, whilst this is still classed as a G99 system which requires a grid connection agreement to be in place prior to installation, this can be fast tracked which is quicker for the DNO to process. The below example is from a domestic installation undertaken in 2023.

20230915 162404 - Tethys Energy

Following the approval of the G99 Fast Track application from the District Network Operater (DNO), we installed the 3.24kWp solar PV system which entailed 8 x JA Solar panels powered by a SolarEdge inverter. The battery system is made up of a GivEnergy AC charge controller with a GivEnergy battery.

Equipment installed:

  • 8 x JA Solar black half cell monocrystalline 405W solar PV modules
  • 3.0kW Solar Edge PV inverter
  • 8 x Solar Edge S440 Power Optimizer
  • 3.0kW GivEnergy AC charge controller
  • 5.2kWh GivEnergy battery

From the DNO’s perspective, the key components are the 3.0kW PV inverter and the 3.0kW AC charge controller as these are the devices which can potentially export onto the grid. These devices must be approved and have a G98/G99 certificate which ensures their compliance with the UK electricity grid. Whilst the total system size is 6.0kW which does require a grid connection agreement under G99, the application can be fast tracked because each individual device is under 3.68kW.

It can get a bit confusing to figure out if a system qualifies for G98 or G99 or fast track. However, here at Tethys Energy, we have been designing and installing solar PV and battery storage systems for over 10 years and have a solid understanding of the DNO requirements for each of our customers projects. This allows our customer to have the peace of mind knowing that their installation is fully compliant with their local DNO’s requirements.

IMG 9108 - Tethys Energy

SolarEdge PV System & GivEnergy Battery set up

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