On Tuesday, 6 days into the Winter 26-27 season, we NESO issued an Electricity Margin Notice (“EMN”). Despite NESO repeatedly telling the market that EMNs are “routine tools” that do not signify a blackout, the following facts are notable:
- It was long: this EMN was initially issued for the period from 3pm to 11pm (later shortened to 4pm to 11pm). NESO described this on X as “the evening peak” – under no interpretation of the market does the evening peak last for 8 or even 7 hours. The length of this EMN was unusual.
- It was very early in winter: EMNs outside the peak of winter are unusual – to have one in what is still considered a shoulder month is not a good sign for the winter ahead.
- The initial response was negative: The first EMN came around midnight showing a shortfall of 1,840 MW. The update just before 7am showed an increased shortfall of 1,880 MW. This is highly unusual – an EMN is a signal to the market that more capacity is needed and it almost always results in additional capacity being available quickly – not necessarily enough to close the entire gap, but to see the shortfall increase after the market has been asked to respond is very rare.
While it is true that an EMN does not signal a blackout, if a capacity-related blackout were to occur it is likely to have been preceded by an EMN, so it is not true to suggest they are not linked. A capacity-related blackout would be one where there was not enough generation to meet demand, as opposed to a system outage triggered by a fault. If NESO didn’t anticipate a capacity-related blackout and had not issued an EMN beforehand it would not be doing its job properly.
NESO itself says system notices are usually associated with periods of higher winter electricity demand. Last winter there were no EMNs at all, while there was just one the winter before, on 8 January 2025. 2026 has been very different, with the first ever summer EMN in June, further notices during the summer and another on 28 September. Now, barely a week later, we have had another.
What actually happened on 6 October?
The first warning came just after midnight. NESO knew as the day began that the market would be short by a large amount for many hours. The current security standard requires NESO to hold enough reserves to cover the loss of the largest infeed which is currently 1,400 MW so this puts the size of the shortfall into context. The original notice also stated that 750 MW of generation was being excluded from the available system margin because of system constraints.
At 7am when the second EMN came, demand for the afternoon and evening was forecast by Amira Technologies to be 33.2 GW at 3pm, 33.9 GW at 7:30pm (Amira’s expected peak) and 25.8 GW at 11pm. I noted these down from the dashboard but unfortunately did not note down the equivalent BMRS forecast. Amira’s forecasts are generally regarded as being highly reliable and widely used as market indicators. BMRS forecasts which I checked in the afternoon had 7pm and the peak – I believe the actual peak was in the middle of the settlement period, around 7:15pm.
An update was issued at 12:53pm when the shortfall had fallen to 679 MW, and another at 2:16pm when it was down to 321 MW, being finally withdrawn at 3:51pm. In the end, there was no blackout (none had realistically been expected) and frequency remained stable through the peak.
NESO’s forecasts for the day were all over the place, highlighting the real issues NESO has with predicting both wind output and demand. Wind output was low at just 25% of this year’s average, and on 6 October it out-turned 1.4 GW below the day-ahead forecast. Luckily NESO also got its demand forecast for the peak wrong, with the peak demand being 921 MW lower than expected – bank error in your favour, collect £200! This meant the net error was only 480 MW rather than a potentially disastrous 2.3 GW had the demand been higher than expected by the same amount.
The day-ahead interconnector nominations indicated that for much of the shortfall period GB would be exporting. This being the case, it was expected that NESO would resolve its shortfall by buying electricity from neighbouring system operators to reduce or reverse these exports, or, where imports were expected, to increase them.
Since May the EU has restricted system operators in trading against the market, so if an interconnector is set to export, the system operator is restricted in the amount of electricity it can buy on that interconnector to 300 MW in any settlement period. Across all interconnectors the aggregate limit is 1,500 MW per settlement period.
As expected, NESO did lean heavily on imports. In its trades for 4:30 pm, IFA alone was set to import 1,336 MW. IFA2, ElecLink and BritNed were also above their respective 300 MW trading limits. These limits exist for a reason – European regulators believe that system operators trading against the market flow distorts the market and for this reason has decided to restrict them. However, over the summer, NESO repeatedly breached these limits as it struggled to balance the system during various heatwaves when wind output was very low. This can only be done with the agreement of the other TSOs.
It shows that normal market arrangements were not enough to resolve the EMN and NESO was forced to intervene on the interconnectors.
As we can see from this later snapshot, within day trades have increased imports, reduced exports and in some settlement periods, flipped the nominations from export to import.
But the interconnectors alone were not enough. At the same time, NESO was forced to pay high prices in the Balancing Mechanism (“BM”). Several units were bid up at prices approaching £1,000 /MWh against a day-ahead price of £275 /MWh in the peak.
By 7:30pm balancing costs for the day according to the LCP Enact dashboard had risen to £14.75 million against an average daily balancing cost of £2.3 million. Neither the full end-of-day balancing costs nor the price of NESO’s interconnector trades are yet known – NESO’s official daily balancing-cost dataset is updated weekly and at the time of writing has only been updated to 3 October.
But regardless of the eventual daily total, paying close to £1,000 /MWh for multiple balancing actions is hardly evidence of an electricity system awash with spare capacity.
The system worked but it was not comfortable
NESO will undoubtedly point out that electricity supplies remained secure throughout yesterday – it said the same about 23 June despite whistleblowers saying otherwise. The absence of a blackout is taken as proof the system is secure. I have compared this to saying that running in the road is safe because you did it a few times and weren’t hit by a car.
The 6 October did not see a blackout, nor was it a near-blackout. The grid was more secure than on 23 June, with frequency remaining inside the operational limits. But that should not obscure what actually happened, and how uncomfortable it was. We had a rare October EMN. We had an unusually long eight-hour EMN window. The margin shortfall initially increased rather than fell after the notice was issued. Wind output was around 1.4 GW below its day-ahead forecast, while demand was 921 MW below forecast – two very large forecasting errors which fortunately offset each other to a significant extent. Interconnector trading limits were breached. High prices were accepted in the BM.
All this happened in early October, with electricity demand nowhere near the levels we could see during a cold winter evening. The electricity system didn’t fail, but neither did it sail effortlessly through an routine autumn evening peak. NESO had to work hard to maintain its operating margin, and benefited from a large demand forecasting error in its favour – imagine if the error had been in the other direction.
NESO’s demand forecasts are getting worse. The day-ahead forecast error can be as high as 5.7 GW – an error that large on a day like 6 October would be disastrous.
To have an event like this so early in the winter is worrying. Peak demand was 35.0 GW (ITSDO – INDO was 32.9 GW). On a typical mid-winter day it would be around 45 GW, while the highest peak demand day last winter reached about 50 GW. On 6 October around 14 GW of biomass, gas, hydro and nuclear capacity was offline for maintenance, most of which would be expected to be available in mid-winter. Most but not all – it would be reasonable to expect 12 GW to be available, which would be helpful if demand was around 10 GW higher as it would be on a normal mid-winter’s day.
But it would not be enough to meet 50 GW of demand. For that we would need all interconnectors to be importing at maximum capacity, and for no large generators to be offline. Unfortunately, the type of weather that leads to 50 GW of GB demand these days would likely be cold and windless both here and in our neighbouring countries.
As my recent gas security report explains, low gas inventories in Europe coupled with low reservoir levels in Norway might make European electricity grids tight and their prices high. This could limit the availability of electricity imports for GB and could even drive exports. While NESO can restrict exports to protect domestic system security, it has no powers to compel imports.
The situation is likely to get much worse
The Government’s Clean Power 2030 Plan would see a greater reliance on wind and solar. Most of the existing nuclear capacity is retiring in March 2030 and March 2032 (following recent life extensions), but by then we may well see some CCGT retirements as 1990s-built plant reaches end of life. The existing biomass subsidies for Drax and Lynemouth are set to expire in March 2027, although there is a transitional extension to March 2031 – this may have to be renewed despite the controversy.
Earlier this year Drax “paused” its carbon capture project until state support can be agreed. I have always been doubtful that carbon capture equipment could be economically retrofitted onto such an old plant as Drax. More recently, the Government has decided not to extend the subsidies for small biomass plants which will all expire by April 2027. These are small units (10s of MW) but the loss of any dispatchable capacity is unhelpful.
By the early 2030s we could have much less dispatchable capacity on the grid. While Hinkley Point C unit 1 is currently scheduled to open in 2030, EDF has indicated this could be 2031 and the issues with the so-called “fish disco” could see it delayed further.
What 6 October shows us is both the value of flexible generation and the danger of assuming it will always be there when needed. Intermittent renewables depend on weather we cannot control while interconnector imports depend on countries we cannot control.
We are building a grid that is increasingly fragile, with market warnings now occurring year-round. It is essential that ministers get a grip on this situation. NESO needs to urgently improve its forecasting – it cannot be acceptable that errors in the GWs are being made. It is also vital that the Capacity Market is reformed to deliver new dispatchable generation even if that means unabated gas – Germany recently received EU state aid approval for 12 GW of new gas generation – and it also needs to be reformed to remove capacity that is not guaranteed such as interconnectors and unproven demand-side response.
Unless ministers address these problems, Britain risks reaching a point where electricity demand cannot reliably be met during periods of cold, still weather. At that stage, the question won’t be how much it costs to keep the lights on, but which consumers will have to be disconnected to prevent the system from failing.
H-E-L-P.
Thanks for this, very interesting analysis. I’m curious as to why you think carbon capture is a struggle for older plants such as Drax – surely an exhaust is an exhaust regardless of age and there are a range of technologies available to handle differing exhaust gas compositions.
I thought current CCS theory is build a liquid air plant, feed a boiler only the pure oxygen from it, then capture and compress all the exhaust gases, being 90+% CO2. If that is the case, retrofitting would be a lot more expensive than a new build.
Thanks to succesive incompetent governments, we all need to be fully prepared for a prolonged blackout. I am.
As it seems that next time … the question won’t be how much it costs to keep the lights on, but which consumers will have to be disconnected to prevent the system from failing … is it fair to answer that the customers who will have to be disconnected to prevent the system from failing will be those customers connected via a so-called “smart meter” which has a built in disconnector switch which can be “switched off” by centrally controlled commands ? REASON: As significant numbers of electricity customers on so-called “smart meter” allegedly enjoy lower electricity bills, then it’s only fair that electricity customers on so-called “smart meter” ought to be disconnected first.
I simply cannot understand why the points you make, which would be perfectly comprehensible to a twelve year old, are beyond the wit of past and present politicians. I only have a few years left but God help my grandchildren.
I totally agree with you. I too worry about my grandchildren.
Thomas … “I simply cannot understand why the points you make, which would be perfectly comprehensible to a twelve year old, are beyond the wit of past and present politicians.”
Could it be because most past and present politicians have an (electricity / energy) comprehension age that matches their shoe size?
Can Lynemouth and Drax revert to coal?
As you end with words which state … the question [next time] won’t be how much it costs to keep the lights on, but which consumers will have to be disconnected to prevent the system from failing … is it fair to answer that the customers who will have to be disconnected to prevent the system from failing will be those customers connected via a so-called “smart meter” which has a built in disconnector switch which can be “switched off” by centrally controlled commands ? REASON: As significant numbers of electricity customers on so-called “smart meter” allegedly enjoy lower electricity bills, then it’s only fair that electricity customers on so-called “smart meter” ought to be disconnected first.
Anyone who thinks that is a good idea to replace compact, centralised power generation technologies that work at ~90% productivity, at large scale and consistently 24/7/365 with “Renewable” technologies that depend on power sources that are dilute, unreliable, widely distributed, non-dispatchable and only work intermittently at a combined productivity of ~18% or less, (actually as low as ~15% across Northern Europe in 2025), must be in error or malign.
The low productivity of Weather-Dependent “Renewables” means that they have to be about 5-7 times larger in nominal face plate value just to contribute the same amount power to the Grid over the year.
Even at scale, “Renewables” are still unreliable, often un-controllably under-producing or over-producing. If the costs to generate equivalent power costs with Weather-Dependent “Renewables” were equivalent, (their costs are much higher when fully accounted for subsidies, Grid connections and other accounting fixes), their power costs significantly more than conventional Gas, Coal and even Nuclear technologies.
A comparison of the direct costs with conventional generators are outlined here:
https://edmhdotme.wpcomstaging.com/the-costs-of-weather-dependent-renewables-against-conventional-power-generation/
https://edmhdotme.wpcomstaging.com/a-few-graphs-say-it-all-for-renewables/
These values still discount the gross fiscal losses that excessive power prices will cost any economy.
• Weather-Dependent “Renewables” are: · dependent on massive subsidies charged to customers
• require costly extended grid linkages to gather power from widely distributed, small scale, power sources.
• very destructive of the environment, agricultural land and wildlife.
But from on now as the warming effect of any added CO2 is virtually saturated further Man-made CO2 emissions causing Climate Change are a non-problem going forward.
https://edmhdotme.wpcomstaging.com/proportions-of-the-temperature-contributions-of-greenhouse-gasses-h2o-co2-n2o-ch4/
Having diligently eradicated its industry by offshoring its manufacturing, the UK only produces ~0.8% of Global CO2 emissions. As far as CO2 emissions are concerned the UK and even Europe are comparatively irrelevant in the context of the relentlessly growing CO2 emissions from the Developing world, particularly from China, India and East Asia.
Weather-Dependent Wind and Solar “Renewables” aren’t effective power sources: at best they can only ever be occasional, intermittent and unreliable fuel-savers.
Given that our demand seems to vary between approx 35GW and 50GW a demand forecast error of about 5GW is always going to be problematic. That about 14GW is presently not available due to maintenance is hugely worrying. How can such a large proportion of our generating capacity be unavailable at the same time? I imagine that keeping an aging power station going will be challenging but we need to do better. Other countries face similar challenges so we can’t rely on imports. Given the (continued) delays at Hinckley, Government needs to swallow the 0 carbon nonsense and start getting some gas power stations built. Get the North sea going and sort Nordstream!
We are being forced to live through a make-believe fantasy based around mandated low-quality (low-ERoEI and inertia-less) energy supplies which are unsustainable without the heavy-lifting capabilities (in mining, mineral processing, steel and concrete production, shipping, …) of the very hydrocarbons they are supposed to replace. We are courting disaster by relying on international interconnectors we don’t control (cheatingly deemed to be “emissions-free”) and batteries whose grid-scale storage capacities are totally inadequate. We are subjected to the massive cheat of firing Drax and Lynemouth with biomass (wood pellets) whose CO2 emissions are higher than coal but have been designated “carbon neutral” by green blob connivance. We are subjected to the pretence that carbon capture and storage will confer benefits which justify its ruinously expensive costs.
The 95% grid decarbonisation “plan” is clearly unachievable without incurring regular rolling power cuts and ruinously high electricity prices yet nobody in authority challenges the roller-coaster to disaster we are being forced to ride with no exit other than crashing into the buffers.
More people need to read Richard Lyon’s excellent but scary new book “The Energy Trap”, available from Amazon. In concise, layman-friendly prose he describes the double-whammy of energy policy delusions by which we are sleepwalking into an economic catastrophe which will totally upend our society, namely mandating the use of Net Zero low-quality energy and sticking heads in the sand on the impending peak oil crisis.
Thanks for another informative post, Kathryn.
“The current security standard requires NESO to hold enough reserves to cover the loss of the largest infeed which is currently 1,400 MW” (1,400MW being NSL infeed)
However, Drax is rated at 2,676MW, and its infeed into our transmission system is (likely to be?) similar. So wouldn’t that be NESO’s LLoL risk?
No doubt NESO will loose this event in the no problems list..
Rather like Inertia monitors?
And as we are not in the Winter Period until Oc31 2026 then the winter forward view of better margins is not applicable yet applies?
Leaving aside the poor forecasting and last-minute scramble for capacity, the net result was 100% utilisation of the 8.8 GW of continental interconectors between 11.00 and 12.30 GMT [bmrs.elexon]. Nuclear and Biomass were also maxed out. There is only so much spare gas (12.5 GW?) now to rescue us in the event of a high-stress winter.
EDF’s Cottam site – the ideal location for a new gas plant – has a planning application for an AI datacentre. EDF is looking to draw an additional 1 GW of grid power for its datacentre in the medium term. NESO’s short-term forecasting may be poor, but there seems to be no long-term forecasting at all.
Do you know why NESO pays £1000/MWh for imports rather than just turning up the gas?
Sorry – just realised that £1000/MWh was the BM price.
When it happens…. How do they decide which areas to disconnect in an emergency?
London first ? Surely not ?
They are supposed to give at least 8 hours notice.
The “Load Block” Method: To achieve equity, the protocol relies on dividing the national electrical demand into 18 distinct “Load Blocks” (each representing roughly 5% of demand). DNOs must rotate disconnections across these blocks in short, controlled increments—typically capped at three hours at a time—rather than repeatedly cutting power to the same uncoordinated areas.
Up to 20% of demand can be culled this way. Some safeguards for hospitals and military sites.
Why are we putting up with these jackass mps
Fantastic analysis.
Huge blackouts in London since you wrote prove you should be managing our grid rather than the philosophy graduate foisted on us to replace the dangerous lunatic Ed Milipede.
Those were power cuts not blackouts – a blackout is an outage affecting the transmission system, and this takes out large areas. A power cut affects the low voltage grid. UK Power Networks, which operates the low voltage grid in London, confirmed various power cuts across the city last week. The impact on the consumer is similar – a power outage – but the causes and responsibilities are different
Who can you rely on? Isn’t that the question. Government? Can they do the right thing? Do they understand economics? With the addition of more and more centralised supply, it can be cheap, if there were no extra taxes added into the system.
Extra taxes added into the electricity grid:
Carbon taxes
Renewable obligations
Land leasing for power generators
Curtailment fees
Grid upgrades and extensions
“Peakers”
CCS “investment”
This is why people should be generating their own power where possible. The grid has been turned into a giant money transfer machine, where electricity is just a by-product.
Payment for non-production, the biggest adverse tax.
But this is why we don’t have a manufacturing economy any more. The electricity grid has been turned into a huge machine, just for the benefit of the power providers.
As the costs increase, the only response is to self-generate.
Many larger power users have saved themselves millions of pounds each annually with solar PV or CHP.
It is time for the government to stop forcing the grid into an uneconomic mess, and just let users fit and use self-generation where they can make it economic.
Centralised planning never worked for Soviet Russia, isn’t it time we stopped the centralised economic “benefits system”, that pays for non-production, taxes to support people who can’t be bothered to invest to do their own insulation to save costs, or move to, or build, a more economic house/building that they can afford to heat etc.
There is a huge difference between factories producing power during the week for themselves, and then having that surplus power available at the weekends for residential, compared with what we have now.
The government has to get costs out of the electricity system. For those that can self-generate economically, with significant savings, the path is clear.
With all the factories that have gone abroad, did they realise that they would have to self-generate to make their business financially viable?
Solar PV can be connected in many different ways with battery charging primarily and then an inverter taking power from the battery, either for supply to the grid or to the end-user. For grid supply, that installation of a battery smooths the supply, no peakers needed, and if installed by an end-user provides a power failure back-up, resilience if foreign powers start targeting the grid.
Self-generation = resilience.
Winter, add in wind for large scale users, giving wholesale pricing at end-user and cheap power at the weekends for residential customers, and for back-up when no sun or wind, CHP.
If there is no sun or wind, doesn’t everyone need CHP, to get the power, if it isn’t available from a central generator of wind or solar PV?
Isn’t the problem that we should have installed CHP instead of >90% efficient boilers? We could have had electricity supplied at the same price as gas, if someone were using/needed the heat.
If you try to miss out a natural development stage by forcing the system economically, you only generate uneconomic outcomes where people abuse the system for their own advantage, or government increases costs of the system to force it to work, to make it exist.
Time to opt out of the system if you know how to do things economically for yourself.
According to the Capacity Market register all of the interconnectors have CM contracts for the CM delivery year commenced on 1st October, for a total of 6,854MW between them. Of course, for that to be a potentially enforceable supply NESO would have to issue a 4 hour in advance CM Notice, which is a tool they have yet to deploy since Jan 8th 2025. Of course, they have to have the right conditions to support the notice: grid constraints might not be excuse enough if capcity is avialable otherwise. I suspect it would cause consternation to have to do something for the £63m/GW (£431.8m in toto) they are earning, and we could well see the sort of reaction that the Irish had during the energy crisis, banning exports altogether.
A history of CM Notices can be found here:
https://gbcmn.nationalenergyso.com/