Streamlining the connection of Distributed Generation projects

12 May
Press release - 12 May 2025
Solar panels in field

Key facts
New grid code modification will streamline the process for smaller distribution network connected generation to connect to the electricity network.
Ofgem has approved a key modification, CMP446, to the Connection and Use of System Code (CUSC).
This modification will allow most embedded electricity generation projects from 1MW to 5MW in England and Wales to forgo Evaluation of Transmission Impact Assessments.

Energy regulator Ofgem has today (12 May 2025) approved a new CUSC modification (CMP446) that will significantly streamline the grid connection process for smaller Distributed Generation projects in England and Wales. 

This change raises the threshold for projects that would otherwise require an Evaluation of Transmission Impact Assessment (TIA), increasing the threshold from 1MW to 5MW, enabling faster connections for small-scale energy projects such as small solar and community energy projects. Some areas of the national network will still require TIA’s to be conducted at the existing limit due to existing network constraints.

Currently projects above 1MW looking to connect to their local distribution network are required to complete a TIA, to assess if their connection would require additional network reinforcements to the national electricity transmission network, in order to support smaller distribution networks. While essential for larger projects, this process has often resulted in delays for smaller projects that could have been avoided.

Today’s CUSC modification will enable smaller projects to connect more quickly, delivering clean, renewable energy to Great Britain’s energy system. The modification is especially beneficial for community energy projects, which often fall under the 5MW mark. Once implemented, these projects will be able to connect quicker and contribute to local renewable energy generation and sustainability goals.

This modification is part of a comprehensive set of connection reforms designed to overhaul the grid connection process and prioritise projects ready to deliver clean energy across Great Britain. This change will directly impact 337 projects (totalling 682MW) currently in the connections queue, allowing them to proceed without the need for a Transmission Impact Assessment. By enabling these projects to proceed at pace NESO and other network operators will be able to dedicate more resource to assessing larger projects over 5MW, which are more likely to have a significant impact on their surrounding network.

Matt Vickers, Director of Connections Reform, NESO 

“This change to the connections process is an important step in supporting future community energy and smaller scale projects to connect to our electricity distribution networks. By raising this threshold, we can unlock the connections process for over 682MW of smaller projects without sacrificing on resilience of our electricity networks.”

About NESO

The National Energy System Operator, NESO, is an independent, public corporation at the centre of the energy system taking a whole system view to create a world where everyone has access to reliable, clean, and affordable energy.

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Notes to editors:

  • CMP446 raises the threshold for Evaluation of Transmission Impact Assessment (TIA), from 1MW to 5MW in England and Wales where it is supported by the electricity network.
  • In areas where fault level issues exist at the transmission network level the TIA threshold will remain at 1MW. Currently this will apply to 39 Distribution Network Grid Supply Points out of the 225 Grid Supply Points that make up the distribution electricity networks across England and Wales.
  • NESO has committed to updating the list of affected sites before every gated window so that all stakeholders are aware of the latest position. NESO will provide the latest information a month before a window opens.
  • In Scotland, a TIA is required for projects above 200kw as the electricity transmission network in Scotland typically operates at a lower level than in England and Wales. Although this new threshold does not affect Scottish projects, NESO’s broader package of connection reforms will benefit projects across Great Britain, ensuring a more efficient connection process for all.