GB Grid Connection Reform, Transmission Impact Assessment threshold to 5MW and what this means for Distributed Renewables

In a previous blog, we mentioned that grid capacity is “arguably the scarcest resource on the planet.” To give a sense of scale, in December 2024 NESO communicated that the connection queue in Great Britain reached 750GW. An extraordinarily high number when compared to the amount of capacity actually connected to the grid today - 75GW.

But things are moving: Connections Reform is coming up and the threshold for Transmission Impact Assessment (TIA) is on the road to increase from 1 to 5MW. In this blog we’ll look into these changes, and see how they will guide the market towards better site level energy planning and modelling, and pave the way for an ever increasing role of behind the meter assets in the energy system.

What’s happening?

Last Wednesday, 29th January, marked the start of the Grid Connection Application Pause, a measure planned by NESO to prepare for the new Grid Connection Reform. In effect, until Ofgem gives a final decision on the reform, the majority of grid connection applications—whether transmission- or distribution-connected—will have to wait. A decision is expected no later than 31st May 2025.

There are a few exceptions to this pause, such as transmission-connected demand projects, or distribution-connected applications under 1MW (as the entirety of their application will be considered by the DNO), more on that on NESO’s website. 

If Ofgem approves the reform, the application process will align with the new Connection Reform.

NESO’s Connections Reform 

Until now, NESO’s framework for grid connection applications has operated on a first-come, first-served basis. In recent years, two major issues have emerged:  

1. Bottlenecks in the queue: Projects essential to achieving net-zero emissions and ready to move forward can get stuck behind large, slow-moving projects requiring multiple revisions. As a result, the queue became unmanageable.
2. Lack of coordinated energy planning: This incremental approach prevents NESO from implementing a cohesive strategy for energy planning and aligning with long-term Net Zero goals.  

To address these issues, the new Connections Reform will replace the first-come, first-connected system with a first-ready, first-needed approach. Instead of rolling applications, NESO will introduce bi-annual application windows. This shift will enable NESO to assess applications holistically and prioritize connection dates for projects deemed "ready and needed." 

But what exactly qualifies as "ready and needed"? 

To receive a “Gate 2 offer”—the only offer to receive a confirmed connection date and a spot in the delivery queue—NESO will assess two key criteria:  

1. Readiness Criteria: This ensures that projects demonstrating readiness—such as securing land rights and obtaining validated planning consent—receive earlier connection dates.  
2. Strategic Alignment Criteria: NESO will use the Government’s Clean Power 2030 Action Plan (CP30 Plan) to determine priority technologies and locations. By aligning projects with the 2030 and 2035 energy pathways, NESO will decide the optimal connection dates for different technologies in the broader context of Great Britain’s energy system.  

One great takeaway from the reform is that ready projects will be prioritised and will no longer have to sit behind slower ones. Once through Gate 2, projects will also need to meet key milestones, and any that fail to do so will be removed from the queue. This is foreseen to enhance the system’s efficiency.

Another, more contentious, key difference in this new system is the introduction of the Strategic Alignment Criteria. Through it, NESO will be playing a much larger role in decision-making and strategic planning than it used to, for example by favouring some technologies over others, which wasn’t previously the case. Some of this insight can be taken from the following chart, which shows the technologies in the connection queue compared to the capacity planned in the CP30 report.

So, what does this mean for energy investments?

Impact on the energy industry

Importance of planning

With the incorporation of the readiness criteria, NESO will aim to accelerate projects that have already completed much of the planning stage before applying for a grid connection point. This ensures that projects are serious and well thought out. This is particularly beneficial for Gridcog customers, who will gain a key advantage through the accurate modelling of their projects—unlike others who may rely on rough estimations. Not only will this strengthen their position with NESO, but it will also build trust with investors, landowners, and partners, ultimately helping to speed up the process.

Importance of maximising connection MW

By comparing all grid connection applications to the CP30 Plan, NESO will inevitably favour applications who do more with less. With proper planning, sites that incorporate co-located assets, such as solar and batteries, can generate significantly more energy and provide greater flexibility within a smaller connection limit. Once again, modeling tools like Gridcog prove invaluable in assessing and optimising the combined impact of multiple assets on a single site.

And what about smaller, Behind-the-Meter projects?

Spoiler alert, for BtM assets, things are looking good. But first, we need a bit more context.

Up until now, all projects above 1MW in England and Wales, even those connected to the distribution network, had to go through NESO for a Transmission Impact Assessment. This requirement has caused significant delays for behind-the-meter projects, sometimes postponing them by up to 10 years.

However, recognising the crucial role of behind-the-meter projects in the energy transition—particularly due to their co-location with demand sites therefore maximising grid connections—NESO has proposed increasing this threshold to 5MW in England and Wales. Ofgem agreed on 17th January 2025 to fast-track the review process, bringing the timeline forward from 1st April 2026 to 2nd May 2025.

So?

Provided this increase goes ahead, we’re expecting a strong increase in Behind-the-Meter interest: Skipping the Transmission Impact Assessment is a clear advantage for projects, and raising the threshold will undoubtedly attract more participants looking to accelerate deployment. Removing this step significantly reduces uncertainty, making behind-the-meter projects more attractive to both investors and owners.

Furthermore, this update aligns with the broader trend of energy regulators increasing the role of behind-the-meter assets in the wider energy system. For example, in this video, we discuss how the recent P415 code modification opens up wholesale market revenue streams to behind-the-meter flexibility assets.

The Bigger Picture

These connection reforms will continue to be refined during Ofgem’s review process, but they are also likely to evolve after the initial implementation to respond to industry uptake and feedback, and to changing industry and market conditions. 

Staying up to date with industry developments is therefore essential to model projects that align with market trends and future shifts.

At Gridcog, our industry team dedicates significant time to keeping up with market changes, ensuring that our software accurately reflects real-world conditions. We take pride in being not just modelling experts, but also energy system experts.

‍

‍