G99 sets out the requirements for connecting generation systems to the Distribution Network. G99 applies to all generation installations over 16 amps per phase (Single phase systems up to 3.68kW and Three phase systems up to 11.04kW). Anything smaller will fall into a G98 application.
Why is G99 important
Following the G99 recommendation ensures generation installations connect to the grid safety and do not compromise network stability, safety or power quality.
How to Apply
Applications for generation over 16amps/3.68kW per phase are required to complete the relevant ENA application form. This is universal practice across distribution network operators (DNOs) such as SP Electricity North West. The type of G99 application form you require depends on the system size. Click on the drop downs below to find out more about each application form.
The application form for G99 up to 50kW is the A1-1 form: Application Form. Along with your application, please also send a Single Line Diagram of your proposed installation.
Once your application has been accepted and the system installed, you'll need to complete and submit:
A3-1 commissioning document
Single line diagram
G100 Form C (if export limitation applies)
If the system your installing doesn't have a fully type tested inverter, you'll need to submit an A2-3 commissioning form
Important: Do not switch on your generation system until these commissioning documents have been reviewed and approved.
If anything further is required as part of your generation installation your SP ENW engineer will you know. This will also be documented in the ‘Distributed Generation Project Specification’ section of your quote letter.
If you are wanting to export, providing the export amount is less than or equal to 30kW the approval letter can be sent to the energy supplier for SEG tariff. For exports over 30kW you'll need to request an export MPAN.
The commissioning form for G99 installations is the ENA G99_A3-1 form:
The application form for G99 over 50kW is the ENA Standard Application Form (SAF): Application Form. Along with your application, please also send a Single Line Diagram of your proposed installation.
Once your application has been accepted and the system installed, you'll need to complete and submit:
A3-1 commissioning document
Single line diagram
G100 Form C (if export limitation applies)
If the system your installing doesn't have a fully type tested inverter, you'll need to submit an A2-3 commissioning form
G5 harmonics report
Confirm that the installation utilises an active front‑end inverter
Important: Do not switch on your generation system until these commissioning documents have been reviewed and approved.
If anything further is required as part of your generation installation your SP ENW engineer will you know. This will also be documented in the ‘Distributed Generation Project Specification’ section of your quote letter.
Please note, As of the 1st January 2026, SP ENW will charge a fee to review commissioning documentation of any generation schemes over 50kW. This fee will include a review of the compliance with G99, a review of any compliance with G100 (export/import limitation scheme), G5 (harmonics) and P28 (voltage step change).
If you are wanting to export, providing the export amount is less than or equal to 30kW the approval letter can be sent to the energy supplier for SEG tariff. For exports over 30kW you'll need to request an export MPAN.
The application form for G99 1MVA and above is the ENA Standard Application Form (SAF): Application Form
Once your application has been accepted and the system installed, you'll need to complete and submit the A3-1 commissioning document, a single line diagram, G100 form C and a G5 harmonics report for approval before the system can be switched on. If there are any limitations on your installation a G100 may also be required but your engineer will advise.
If the system your installing doesn't have a fully type tested inverter, you'll need to submit an A2-3 commissioning form alongside the single line diagram.
For exports over 30kW you'll need to request an export MPAN.
‘Witness testing’ is where we, SP Electricity North West, the network operator for the North West, attend the site of your generator to witness your commissioning engineer test the protection systems associated with your generator and ensure they operate correctly.
