Long Duration Electricity Storage (LDES) is an increasingly important part of our energy system. NESO advice shows we need to increase the amount of storage on the system over the next few years. These assets let us capture energy from excess renewables when the wind is blowing and sun is shining and store this for when customers need it.

Ofgem has designed and is running its first ever window for cap and floor support to encourage the development of LDES projects, applying the successes of the similar schemes we have run for many years to encourage the development of interconnectors to other countries.

We were pleased with the very strong set of applicants we received for Window 1 with over 70 projects of nearly 30 GW participating in the Project Assessment. We have completed a thorough project assessment to select the best projects to meet system need. We are pleased to set out the results of that assessment today, with a varied portfolio of projects which we are minded-to support to ensure we are developing the clean power system for the future.

Beatrice Filkin

Director of Major Projects
Ofgem

Read the full document… https://consult.ofgem.gov.uk/energy-generation/ldes-window-1-minded-to-decision/supporting_documents/ldes-window-1-minded-to-decisions-consultationpdf

Thanks to u/Intrepid-Pen-3112 for the heads up on this!

I'm officially changing my nomenclature from "VRFB" to "VFB". Poor "Redox" will have to remain implicit.

Hi everyone.

The Cap and Floor minded-to decision list (i.e. the initial decision list, which I'll refer to as the IDL) was released yesterday. Out of 16 selected projects, only one utilises VFBs: the 520 MWh Frontier Legacy project. Assuming the 50-50 split between VFBs and ZBBs goes through, that's 260 MWh of VFBs.

Looking at posts and comments on various forums as well as the immediate reaction of the share price, the prevailing sentiment has been one of disappointment, frustration, and sometimes even rage. I have to say that I don't share that sentiment, and am perfectly satisfied with the result.

I think that the Flexbase announcement and the immense hype from Cap and Floor (part of which, I suspect, is my own doing) have somewhat bloated the scale of expectations. For one, 260 MWh is a larger capacity than Invinity's entire deployed fleet—an accumulation of nearly a decade of previous sales—combined. Before the Pacific Steel announcement, it would've been more than 10 times larger than Invinity's largest contracted sale. If the project comes to financial close as envisioned, it would be a fantastic stepping stone for a company as small as they currently are.

Furthermore, and just as important: this window was VFBs at their absolute weakest vs LIBs at their absolute strongest. Since the end of 2025, lithium and copper prices have gone up, demand is catching up to the previous oversupply, and China is completely axing its export tax rebates starting 2027. Meanwhile, Invinity's cost reduction program is progressing rapidly, vanadium prices remain low (perhaps too low, but that's another story), and Matt Harper even hinted at improvements to performance and efficiency during the FY25 report. After the top 13 in this round, competition became real tight, and Ofgem already expressed their desire for more windows. It won't take too much narrowing of the gap for VFBs to be in a materially better position.

Had the Flexbase deal not been announced, and had we not been receiving a steady stream of positive and promising news both from Invinity's core operations and the VFB market as a whole, I probably would have been more concerned about this result. The optics would then have been "a company with a product that nobody seems to want, clinging to the good graces of their local government for a contract." But that's not the case. C&F is one of many opportunities for Invinity, and they (probably) managed to get a nice big contract out of it, which is all I personally wanted out of it. Their success was never dependent on a single government scheme, and I believe they will get additional, large contracts from other opportunities (particularly from the US in the short term).

With all that being said, I definitely did have hopes that they would get more out of this window, and VFBs scored less than I expected compared to other tech. Many of the reasons for that I'll admit I don't really understand, so I think it's worthwhile to look over the results and see where things went well and where they went poorly. I'll first give on overview of how the assessment was performed and then focus on VFBs.

The Assessment

Everything written here is based on the published minded-to decision document, which you can read here.

The process was essentially one main assessment step, followed by two modification steps. The main step was the Economic Assessment (EA), which was by far the most important assessment of the scheme and served as the backbone of the IDL, providing an initial ranked list of projects. It was followed by the Financial Assessment (FA), which took the EA results and crossed out any projects whose revenue model Ofgem deemed too risky. Lastly, the Strategic Assessment (SA) was for Ofgem to take the modified list and apply any further modifications based on principles that were not included in the previous stages. The output of the SA was the final list.

The Economic Assessment

After taking the weighting of the different components into account, the EA ranking was made in the following manner: projects were ranked by how many points they received. A project could receive up to 247 points, divided as follows:

Here are brief descriptions of what each component described:

• Monetised Impact: this was determined by the benefit-cost ratio (BCR)—the ratio of the present value of various economic benefits of the project, detailed on pages 22-23, to the present value of the costs of the project (DevEx, CapEx, OpEx, and RepEx), calculated with a discount rate of 3.5% real over a 25-year appraisal period. The costs were taken from the P50 (most probably) estimates of the projects. To account for the different lifetimes of differing technologies, Ofgem assumed a fixed "economic lifetime" for each technology type, which they say "reflect the point at which a project would be expected to require significant further capital investment to continue operating." They then added a "terminal value" to reflect the added value from the operation of a project beyond 25 years up to its lifetime and used it to offset some of the costs. The lifetimes were assumed as follows:

https://preview.redd.it/t04hpkr3au9h1.png?width=1102&format=png&auto=webp&s=11ced4477bdabbac2eedd736990318e1cc26e746

• Security of Supply: "the contribution of each project to system adequacy." Basically a measure of a project's duration, energy capacity, and efficiency. Duration was by far the biggest deciding factor: if project A had a longer duration than project B, project A nearly always got a higher SoS score.
• Avoided Renewable Curtailment: self-explanatory.
• System Operability: the project's ability to perform additional grid-stabilising services: frequency response and reserve, stability, voltage control and restoration.
• Wider Economic and Social Impacts: "considers impacts not captured in monetised or other non‑monetised metrics, including effects on local communities, the UK economy and the energy sector."
• Real‑time Flexibility: Essentially a measure of a project's short-term power capability above continuous capacity (can it briefly charge/discharge at a higher MW than its rated capacity).
• Option Value: potential for future benefits. Mainly expansion capability and adaptation over time.

The Financial Assessment

The FA ended up having one role: to check whether, for each project, projected revenue lies above or below the "risk threshold" defined as 0.6 of Ofgem's calculated floor. Then take the ranked list from the EA, and push all the projects that were below the threshold to the bottom, keeping their internal ordering. In other words, the FA "crossed out" any projects that Ofgem deemed to present too large a risk of over-reliance on the floor.

The Strategic Assessment

A chance for Ofgem to make further modification to the list that were not captured before. It tested the projects for deliverability, interdependency, as well as their performance across a set of unfavourable future scenarios. In the end, the only modification was the addition of Frontier Legacy to the IDL, motivated by the desire for technological diversity.

Technological Comparison

Starting with the EA, to get a rough idea of the relative scoring of the main technologies (PSH, LIB, VFB/Zn, VFB), I averaged the EA scores along the various components over the top 35 ranked projects. This allowed me to roughly compare the scoring of the top performers along each category. Since none of the pure VFB projects made it that far up, I averaged across all five of them. The results were as follows (split into 2 tables for readability):

Pure VFB scored the worst overall, followed by VFB/Zn, LIB, and PSH. The same ranking holds for Monetised Score (BCR) alone. VFB and VFB/Zn scored best on WESI (unsurprisingly), and decently well on ARC. VFB scored decently well on OV, and VFB/Zn scored decently well on SO. Both scored poorly on SoS and RTF.

As for the RTE (Table 6 on page 70), The LIB projects got values between 85-91%, PSH got values around 80%, the pure VFB projects all got values of 69%, and the VFB/Zn projects all got 62%.

At the FA, no LIB projects were deemed below the 0.6*floor threshold. 2 PSH projects out of 5 were below the threshold, as well as 7 VFB/Zn projects out of 16. All 5 VFB projects were deemed below the threshold (except for Deeside, which provided no data and so got automatically removed).

At the SA, the PSH projects that were above threshold got decent Scenario-analysis (SA) scores (around 0), while the other two got -23. The VFB projects got between -25 to +20. The VFB/Zn projects ranged from -24 to +7, with the exception of Frontier Grange Lane that got -60 and Frontier Legacy that got -149. The LIB projects had the largest variations, ranging from -77 to +78, with two major outliers getting -123, -156.

As for deliverability, the PSH projects all got "Green" deliverability ratings, and the rest got a mix of "Green" and "Amber".

Thoughts

As I mentioned above, it still puzzles me that VFBs scored as low as they did. In several aspects.

The consistently low scores of the VFB and VFB/Zn projects in the monetised assessment as well as the fact that all five VFB projects were assessed to be below the FA threshold, even though the submitted data ranked them above, leads me to believe that the cost assumptions of the VFBs were very unfavourable. At £200/kWh, the LCOS difference between the VFBs and LIBs should not have been that big (or even negative in the first place), especially with the longer regime length of the VFBs and especially with a discount rate of only 3.5% real. This is further supported by the fact that the PSH projects dominated the BCR scores, in spite of their higher upfront cost and lower RTE compared to LIBs, presumably because of their longer regime lengths.

Speaking of regime lengths, the "economic lifetime" characterisation strikes me as particularly odd. For one, it seems very lenient on LIBs, giving all of them an economic lifetime of 25 years. They say this lifetime does include RepEx, but it also assumes the projects can go 25 years "without significant further capital investment" on replacement, which seems optimistic.

More importantly, for such an important factor in the assessment, this broad characterisation appears overly simplistic. It really seems like something that should be determined on a project-by-project basis. The lifetime of a given project could vary drastically depending on a variety of factors: which vendor do they source their batteries from? What is the rated cycle life/optimal longevity conditions of those specific batteries? Which services is the project planning to provide? How long will it be in a deep charge/discharge state? How much cycling is it planning to do? What is the battery duration? A 16-hour battery will obviously have a different lifetime than an 8-hour battery if it uses the same tech and is under the same environmental conditions and load profile. Ignoring all that for a single overarching number seems oddly irresponsible.

I also can't help but question the assumptions on the performance of the VFBs. The low BCR score (this time looking at the numerator) again suggests that low capabilities were assumed. There are also the strangely low SO scores of the VFB projects. They were deemed not only to perform significantly worse than LIBs for services like frequency response, stability, and voltage control, but were even ranked significantly worse than pumped hydro! Comparing them to the VFB/Zn projects, they were also deemed significantly worse than ZBBs in this regard. This simply doesn't fit with anything I know (or anything that has been published, as far as I could find) about VFBs.

There is also the matter of duration. Ofgem ended up putting great emphasis on it. Not only did the longer duration project achieve a particularly high BCR score, in contrast to the more common "diminishing returns" market consensus(suggesting that the benefit assessment greatly rewarded longer duration), but additionally 47.5 of the points were given by SoS, which is mainly a duration measure. With this in mind, I wonder why all VFB and VFB/Zn projects were only 8 hours (including Hagshaw, apparently), when Endurium is already capable of going up to 18.

I can only make guesses about the reasons for all this. For cost, one possibility is that, since the £200/kWh is currently a goal for 2028 and not a guarantee, Ofgem treated it as a P10 price (the optimistic projection that had no impact on the scoring), while the P50 pricing on which the BCR and FA scoring was based had been taken to be closer to the current amount, which is much less competitive. Another possibility is that Ofgem's Cost Assessment process (used for the final cost assessment) significantly increased the submitted P50 costs through pessimistic assumptions. It's also worth noting that EOL value (particularly the vanadium electrolyte) was not considered during the BCR cost assessment, though it was considered in the FA.

For performance, there is basically zero data nowadays on large-scale VFB deployments and deployments of latest-gen iterations of the tech, especially rigorous data taken by reputable third parties. It's therefore possible that the experts consulting Ofgem would have had to rely on old and fractured performance metrics of dubious reliability and extrapolate them to the scale of the C&F projects. If they had then taken the conservative performance assumptions to remain on the safe side, it could explain the low assumed performance capabilities of the VFBs.

The duration issue could be explained if Ofgem's decision to reward longer durations so heavily was taken late in the assessment process (which seems to be the case), while the VFB projects tried to remain on the safer financial side by sticking to the "lower" 8h durations.

If these guesses are close to the truth, that means we have a lot to look forward to. As time passes, Invinity will move closer to their cost goals and thus de-risk the cost assumptions, more data will be gathered on new-gen VFBs (like the PNNL's currently ongoing measurements), and the VFB projects will have a better idea of Ofgem's priorities and could optimise their plans for the next time, all of which will lead to drastically better scoring in subsequent windows. One positive development is that Ofgem elected to include Frontier Legacy in the IDL during the SA, showing that they do place a fair bit of importance on technological diversity and perhaps Invinity in particular.

At any rate, we are now at the feedback stage of the IDL, which will go on until 7 August, with the final decision list (FDL) to be published in autumn (presumably near the tail end of 2026). I'm sure that many industry experts and stakeholders much more knowledgable that I am will submit their input on the process and identify any misjudgement or error that might've occurred. Though I'm not expecting any significant change between the IDL and the FDL, it will be very interesting to see how the scoring of VFBs changes in subsequent windows.

26 June 2026

Invinity Energy Systems plc

("Invinity" or the "Company")

Update on UK LDES Cap and Floor Scheme

Invinity VFB technology selected by Ofgem to progress under scheme

Invinity Energy Systems plc (AIM: IES), a global leader in vanadium flow battery technology, notes today's announcement from Ofgem of its "minded-to decisions" for Window 1 of the UK LDES Cap and Floor Scheme and the inclusion of the Frontier Legacy project on this list. This project has a total capacity of 520 MWh and is currently expected to be split approximately equally between Invinity's vanadium flow battery technology and zinc-halide battery technology.

The Company views today's announcement positively and notes Ofgem's specific comment that the inclusion of Invinity's vanadium flow battery technology in the Frontier Legacy project was a key factor in Ofgem reaching its "minded-to decision". The Company sees this as yet another key validation of Invinity's technology and the role it has in delivering vital Long Duration Energy Storage capacity to the UK grid and globally.

The Company retains its belief that projects specifying Invinity technology represent clear alignment with the UK's Industrial Strategy by supporting domestic supply chains, enhancing energy security, and growing a UK-manufacturing base for LDES.

Invinity will now work to support Frontier Power in this process to advance this project towards financial close over the coming months. The Company notes that, while management retains a high degree of confidence, there can be no assurance that financial close will be achieved in the form currently envisaged, if at all. 

Jonathan Marren, Chief Executive Officer at Invinity said:

"Ofgem's announcement today, particularly their specific reference to Invinity technology's role within the scheme, underlines the continued progress we are making as a business both in the UK and globally.

"The Company views the cap and floor programme accelerating the benefits of longer duration storage for the UK market as a significant national step in the context of a global market experiencing strong growth of 49% year-on-year. Of the 393 GWh^(1) grid scale energy storage expected to be installed globally in 2026, 8.3 GWh (2% of the global total) is in the UK, with 58 GWh (15%) and 19 GWh (5%) expected in the U.S. and in Europe (ex UK) respectively. On a broader basis, we are also currently seeing significant traction in both UK and global C&I and data centre sectors both directly and through industrial partners. The Company therefore remains extremely positive about its prospects for growth."

Stay up to date with news from Invinity. Join the distribution list for the Company's monthly investor newsletter here. 

^(1) Benchmark Q2 2026 Battery Energy Stationary Storage Forecast

The Competition Appeals Tribunal released its judgement in the Zenobe vs GEMA case. Every single one of Zenobe's arguments were shot down. The tribunal determined that the September publication did not constitute a subsidy decision within the meaning of the Subsidy Control Act (SCA), that the February decision to adopt the scheme indeed superseded the September publication, and that the adoption was properly taken pursuant to s. 10P of the Electricity Act 1989 (as amended by the Planning and Infrastructure Act 2025).

This eliminates this threat to the Cap and Floor scheme entirely and sets a legal precedent that eliminates any future threats based on the SCA.

You can read the full ruling here.

Under Joint Proposal Development Agreement, Invinity and FNUBP will advance energy storage projects across Canada with focus on Indigenous leadership, participation and long-term economic benefit.

Monday 22 June 2026

Invinity Energy Systems is pleased to announce a strategic collaboration with the First Nations Utility Batteries Partnership (FNUBP), an Indigenous-led and Indigenous-owned development corporation focused on delivering long-duration energy storage projects across Canada.

Under a newly executed Joint Proposal Development Agreement (JPDA), Invinity and FNUBP will work together to identify, develop, and advance battery energy storage system (BESS) projects to support grid reliability, renewable energy integration, and long-term decarbonization objectives, including recent participation in PEI Energy Corporation’s RFEOI for BESS, New Brunswick Power’s REOI for BESS, and BC Hydro’s capacity procurement initiatives expected to follow its Capacity Request for Expressions of Interest (RFEOI).

Supporting Indigenous-Led Energy Infrastructure

FNUBP was established to initiate, develop, construct, and ultimately own battery energy storage facilities, with a strong emphasis on Indigenous leadership, participation, and long-term economic benefit. Through this collaboration, FNUBP will act as lead developer, managing commercial, regulatory, siting, and financing activities for proposed projects.

Invinity has been selected by FNUBP as its long-duration energy storage technology provider, reflecting the suitability of their our vanadium flow battery systems for utility-scale applications that require durability, safety, and long operational lifetimes. These, and other qualities specific to Invinity’s BESS equipment, align well with the values of Indigenous Communities.

“This collaboration reflects our shared commitment to building resilient, future-proof energy infrastructure in partnership with Indigenous-led organizations. Engaging FNUBP’s development expertise to deploy Invinity’s made-in-BC long-duration batteries will accelerate the delivery of robust, reliable low-carbon infrastructure. With Canada embarking on a new national electricity strategy, this partnership is timely in proving how bold capacity goals can be met effectively and efficiently by building partnerships among governments, industry and First Nations.”

– Matt Harper, President, Invinity Energy Systems

Enabling Long-Duration Energy Storage at Scale

As part of the agreement, Invinity will supply long-duration energy storage solutions based on its Endurium™ vanadium flow battery platform for projects developed by FNUBP. The parties will collaborate closely on technical design, system optimization, and proposal development to ensure projects are well-positioned to meet customer requirements, including those of utilities and renewable energy generators.

The collaboration is expected to support a portfolio of long-duration energy storage projects across multiple sites, with a particular focus on British Columbia and potential participation in utility-led procurement processes, including capacity-focused solicitations.

Vanadium flow batteries are well-suited to long-duration applications due to their ability to deliver energy over extended periods, their high cycle life, and their inherent safety profile—attributes that are increasingly important as BC Hydro and other utilities seek firm, dispatchable capacity to complement intermittent renewable generation.

“BC Hydro’s Capacity RFEOI highlights the growing importance of long-duration storage as part of the province’s future electricity system,” said Mike Wise, Partner at FNUBP. “Working with Invinity allows FNUBP to pair Indigenous-led project development with world-class, proven long-duration storage technology, positioning our projects to support system reliability while creating meaningful, long-term value for First Nations and their communities.”

– Mike Wise, Partner, FNUBP

A Platform for Future Growth

Beyond British Columbia, Invinity and FNUBP have also agreed to explore opportunities to collaborate on long-duration energy storage initiatives in other provinces and through future procurement programs across Canada.

By working together from early-stage project development through proposal submission and technical definition, the collaboration is designed to create clarity, alignment, and efficiency as projects move toward construction and operation.

“This agreement establishes a strong foundation for long-term collaboration,” added Harper. “It demonstrates how technology providers and Indigenous-led developers, working together, can enhance our utility capacity while accelerating both energy sovereignty and clean energy deployment at scale.”

About Invinity Energy Systems

Invinity Energy Systems plc is a world-leading manufacturer of vanadium flow batteries for energy storage. Built in our factories in Canada and the UK, the Company’s proven, commercialised, longer duration energy storage technology has been deployed at scale and dispatched gigawatt-hours of electricity for customers across the world.

Invinity’s safe, scalable and durable battery technology is a trusted and safer alternative to lithium-ion batteries. Endurium VFBs are engineered for heavy-duty, high throughput applications, they don’t wear out, cannot catch fire and are designed to be operated for 30 years or more. Our products address the challenges of our global energy system, unlocking the power of renewable generation by delivering energy storage without limits.

About First Nations Utility Batteries (GP) Inc.

First Nations Utility Batteries (GP) Inc. is an Indigenous-led development corporation focused on advancing turnkey development and Indigenous ownership of BESS in British Columbia and across Canada. FNUBP’s mission is to enable resilient, low-carbon energy infrastructure while supporting Indigenous leadership, participation, and long-term economic outcomes.

Contact: Mike Wise, Partner, FNUBP (mike.wise@fnubp.ca)

Read the full press release here…

https://invinity.com/invinity-first-nations-utility-batteries-partner/

P.S. Thanks for the heads up on the press release u/Adgorn_!