The Great Energy Displacement – Part Two

The Capacity Illusion: What Britain Can Actually Generate When It Matters

Britain’s electricity debate is dominated by enormous gigawatt figures. But planned capacity is not connected capacity, installed capacity is not actual output, and actual output is not firm power. Once those distinctions are made, Britain’s electricity transformation looks very different.

In Part One we looked at what happened as Britain abandoned coal while global coal consumption remained close to record levels and British industrial energy consumption fell to historic lows.

Part Two turns to the electricity system itself, because one of the biggest sources of confusion in the energy debate is the way the word “capacity” is used.
We constantly hear that Britain has built tens of gigawatts of renewable capacity, that another enormous quantity is in the pipeline, and that still more will be required to meet Clean Power 2030. The figures sound impressive. But there is a fundamental problem: a gigawatt proposed on paper, a gigawatt with a connection agreement, a gigawatt physically installed and a gigawatt actually generating electricity are four different things.
Until we separate them, it is almost impossible to have an intelligent debate about energy security.
The headline number is not the power coming out of the system
The latest DESNZ statistics report 66.0 GW of installed renewable electricity capacity in the UK at the end of the first quarter of 2026. That includes wind, solar, hydro and bioenergy, and it represents an extraordinary expansion compared with the electricity system of twenty years ago.

But 66 GW does not mean Britain has 66 GW of renewable electricity available whenever it needs it.
Nor does it mean 66 GW is flowing across the national transmission network. Much solar and other smaller-scale generation is embedded within distribution networks rather than directly connected to the transmission system. Elexon explicitly distinguishes embedded generation as electricity production connected directly to distribution networks.

Most importantly, “installed capacity” is a nameplate measure. Ofgem defines Total Installed Capacity as the maximum capacity an installation could operate at on a sustained basis assuming the source of power required to generate electricity were available without interruption. That qualification is critical for weather-dependent generation.

A 500 MW solar development therefore does not mean 500 MW is continuously available to Britain’s electricity system. It means the installation has a theoretical maximum generating capability of around 500 MW under appropriate conditions.
The same applies to wind.
That is why we need to stop treating headline gigawatts as though they were electricity sitting on a shelf waiting to be switched on.
Look at what Britain has actually achieved
NESO gives us something much more useful than a headline capacity figure: actual generation records.
Britain’s record wind output reached approximately 23.9 GW on 25 March 2026. Solar subsequently reached a record 15.4 GW between 12:30 and 13:00 on 23 April 2026.

Those are impressive outputs.
But notice what they also demonstrate.
Britain can have tens of gigawatts of installed generating equipment without anything close to that full nameplate capacity appearing as electricity at a particular moment.
We must also be careful not to commit the opposite statistical error: the 23.9 GW wind record and 15.4 GW solar record cannot simply be added together, because they occurred at different times under different weather conditions.
That is exactly the point.
The electricity system does not receive the theoretical maximum of every technology simultaneously.
It receives whatever each technology can actually produce at that particular moment.
That is the number that matters to the system operator.
DESNZ’s own figures show the gap
The annual statistics tell the same story.
DESNZ explicitly warns that technologies with a large share of installed capacity do not necessarily have a similarly large share of generation because their output depends on their load factor — the proportion of their theoretical maximum annual generation that is actually realised.
In 2025, DESNZ calculated load factors of approximately 11.1% for solar PV, 24.1% for onshore wind and 36.4% for offshore wind.

That does not mean these technologies are failing. They are operating according to the availability of their energy source.
But it does mean something extremely important for policy.
When somebody says Britain has installed another 10 GW of renewable capacity, the public should not hear:
“Britain now has another 10 GW of electricity available whenever required.”
It doesn’t.
The real question is how much electricity that capacity produces, when it produces it, where it is connected, whether the network can transport it and what other generation must remain available when its output falls.
That is a much more complicated calculation.
Installed does not mean transmission-connected
There is another distinction that needs to be made much more clearly than I did in the original version of this article.
Britain does not have one simple national pool into which every generator pours its full nameplate output.
Generation can be connected to the national transmission network or embedded within regional distribution networks. Connection agreements also define how much power a station is entitled or physically able to export.
NESO defines Connection Entry Capacity as the maximum physical capability of the transmission connection assets at a site. It separately defines Transmission Entry Capacity, or TEC, as the level of transmission access held by a power station.

That distinction matters enormously.
A project’s generating equipment can have one nameplate rating while its connection or permitted export capability is another.
Then there is the queue.
For years Britain accumulated an electricity connection queue containing more than 700 GW of projects. Nobody seriously believed 700 GW of generation was already operating. NESO itself says the old queue had grown to around four times the amount needed for 2030 and included projects waiting years to connect.

This is why headline announcements about “X GW in the pipeline” must be treated with extreme caution.
A project can be planned.
It can receive consent.
It can hold a connection agreement.
It can appear on a capacity pipeline.
And it can still be years away from producing a single kilowatt-hour.
NESO’s current TEC register makes the distinction explicit: its MW Connected field records capacity actually connected to the National Grid and remains at 0 MW until a project is built and connected.

That should become one of the central facts of this series.
Capacity, connection and generation are three separate tests
So when any politician announces another enormous renewable-capacity figure, there are three immediate questions we should ask.
Has it actually been built? Is it actually connected? And what electricity does it actually produce?
Then comes a fourth:
How much of that output can reasonably be depended upon during the period when the system is under greatest stress?
That is where de-rating enters the picture.
DESNZ does not use the full nameplate capacity of wind and solar when assessing security of supply. In its 2025 electricity statistics, wind, small-scale hydro and solar were explicitly de-rated to account for intermittency so they could be compared more meaningfully with conventional generation.

Against the much larger headline installed-capacity figure, DESNZ calculated total de-rated renewable capacity at 27.7 GW in 2025, including only 14.1 GW attributed to wind and 3.7 GW to solar under that methodology.

Again, that does not mean all the remaining capacity is worthless.
It means something much more precise: its contribution to security of supply cannot be assumed to equal the number printed on the nameplate.
That distinction should be at the centre of Britain’s electricity debate.
Why the old system behaved differently
This is where the loss of coal and older nuclear generating stations becomes important.
Coal stations had environmental disadvantages, but their fuel could be stored and their generation scheduled. Gas stations can similarly be dispatched when required, assuming fuel and plant availability. Nuclear operates differently but nevertheless provides large quantities of comparatively predictable generation.
Wind and solar introduce a fundamentally different operating characteristic.
The grid operator cannot order the wind to increase because electricity demand has risen.
It cannot delay sunset because the evening peak has arrived.
Consequently, Britain is not simply replacing one megawatt of conventional plant with one megawatt of renewable plant.
It is constructing an electricity system in which large quantities of energy are produced when renewable resources are available while other technologies and system services have to provide the flexibility needed when supply and demand diverge.
That is why the distinction between energy and capacity matters.
Wind generated enormous quantities of electricity in 2025. Solar produced a record amount too. DESNZ recorded approximately 153 TWh of renewable electricity generation during the year.

But an electricity system is not kept secure by asking how many terawatt-hours were produced between 1 January and 31 December.
It is kept secure by ensuring there is enough power available at every particular moment within that year.
The cold winter test
That difference becomes most visible when demand is high and renewable output is weak.
Britain’s electricity demand can rise sharply during cold winter weather. NESO recorded a 2025 annual high of approximately 45.9 GW at 5pm on 9 January, while DESNZ’s broader winter peak measure reached 51.5 GW. The different figures reflect different statistical definitions, but both demonstrate the scale of winter requirements.

Now compare that with the characteristics of weather-dependent generation.
Solar reaches its strongest output during daylight and disproportionately in spring and summer. Wind output can range enormously depending upon weather conditions. Neither can be dispatched simply because demand has reached its annual peak.
This is why gas continues to matter.
In 2025, despite the elimination of coal and continued renewable expansion, gas generation increased to 93.2 TWh, representing around 31.8% of total UK electricity generation. Nuclear output, meanwhile, fell to 35.9 TWh, its lowest level since the 1980s.

So while political attention focuses on renewable nameplate capacity, the physical electricity system still requires large quantities of controllable generation.
The real system is bigger than the renewable headline
Britain’s future electricity system is therefore not simply:
wind + solar = electricity.
It is wind and solar plus gas, nuclear, biomass, hydro, pumped storage, batteries, interconnectors, demand response, balancing services, network reinforcement and increasingly sophisticated system-management technology.
Every one of those elements performs a different job.
Batteries are particularly useful for rapid response and short-duration balancing, but power rating and energy storage are again different things. A battery described as “1 GW” tells us its potential discharge rate, not how many hours it can sustain that output.
Interconnectors are useful too, but an interconnector is a means of transporting electricity rather than a source of primary generation. Its availability depends upon the cable, market conditions and electricity being available at the other end.
Likewise, installing a wind turbine does not guarantee the surrounding transmission network has unlimited capability to export its output. NESO’s Grid Code explicitly recognises System Constrained Capacity — capacity that is unavailable because of a system constraint.

These details matter because they expose how misleading the headline figures can become.
We should stop measuring the transition in nameplate gigawatts
This is the change I think we need to make to the argument.
The headline should not be:
“Britain has 66 GW of renewable power.”
That wording invites the reader to assume 66 GW is available power.
A more accurate statement is:
Britain had around 66 GW of installed renewable generating capacity by Q1 2026, but installed nameplate capacity is not the same as transmission-connected capacity, export capability, actual output or dependable capacity.
That one sentence changes everything.
Then put the actual records beside it:
Headline renewable installed capacity: 66 GW.
Record wind output: 23.9 GW.
Record solar output: 15.4 GW.
And make absolutely clear:
The wind and solar records occurred at different times and cannot be added together.
Then put the annual utilisation figures beneath them:
Solar load factor in 2025: 11.1%.
Onshore wind: 24.1%.
Offshore wind: 36.4%.

Now the reader can see the problem without us having to exaggerate anything.
The Government’s own statistics prove that capacity is not generation.
NESO’s own connection data prove that contracted capacity is not necessarily connected capacity.
And actual system records prove that nameplate output is not the electricity Britain receives continuously.
That changes the question Britain should be asking
The debate should therefore stop celebrating every additional gigawatt as though it were another gigawatt of firm electricity supply.
Instead, every proposed generating project should be tested against a much more rigorous chain:
What is its nameplate capacity? How much export capacity does its connection actually allow? When will that connection exist? What is its expected annual generation? What has comparable technology actually produced? What contribution does it make during winter system stress? And what additional network, storage, balancing or backup capacity is required around it?
Only after answering those questions can we begin to understand what the project actually contributes to Britain’s electricity system.
This also exposes the weakness in using huge pipeline figures to demonstrate progress towards Clean Power 2030. NESO’s old connection queue exceeded 700 GW precisely because a queue entry was not the same thing as a deliverable power station. The connections reform programme was created because that distinction had become impossible to ignore.

Britain does not have an electricity shortage because it lacks impressive numbers on spreadsheets.
It has an increasingly difficult engineering challenge because the numbers on those spreadsheets have to be converted into built assets, functioning connections, transportable electricity and dependable supply.
That is what matters.
And it is why the loss of firm power deserves much greater scrutiny.
Britain has eliminated coal, nuclear output has fallen sharply, industrial demand has fallen, and yet gas remains indispensable to the electricity system. Meanwhile, enormous new quantities of renewable nameplate capacity are being planned alongside an equally enormous programme of transmission reinforcement, storage, interconnection and system flexibility.
The correct question is therefore no longer:
“How many gigawatts of renewable capacity has Britain built?”
It is:
How many dependable gigawatts can Britain actually deliver to consumers when they are needed — through connections that physically exist and through a network capable of carrying the power?
That is the measure we should use.
Not the headline.
Not the planning application.
Not the connection queue.
And not the number printed on the turbine, solar farm or battery proposal.
The electricity that actually reaches the system is what counts.
Next: Part Three — The Deindustrialisation of Britain
And there is another uncomfortable dimension to all of this. Britain’s electricity demand might appear easier to satisfy partly because industrial electricity consumption has collapsed to levels last seen more than forty years ago.
In Part Three we will follow that disappearance: steel, chemicals, manufacturing, industrial electricity prices and imports — and ask whether Britain has been solving part of its energy problem by gradually removing the industries that once required the energy.

Sources: DESNZ, Energy Trends June 2026; DESNZ, Digest of UK Energy Statistics 2026, Chapters 5 and 6; NESO, Transmission Entry Capacity Register; NESO, Grid Code Capacity Terms; NESO generation records, April 2026; Ofgem, Renewables Obligation Annual Report.

Shane Oxer.   Campaigner for fairer and affordable energy