If the government achieves its targets for renewable electricity capacity for 2030, will it meet its objective for virtually decarbonising the GB grid? Other calculations are more optimistic but this note suggests that in all probability the answer is no.

I looked at the last year (May 2025 to end April 2025) and multiplied the output of solar and wind generators in each half hour period to reflect the proposed increase in capacity and possible improvements in yield per megawatt of capacity. I also amended the output of nuclear power stations to reflect the closure of two units and I added the possible ouput of NZT, the proposed new gas fired power station with carbon capture.[1] In addition, I assume a 10% increase in total electricity demand resulting from the use of EVs and heat pumps.

This analysis shows that solar, wind, nuclear and hydro would cover about 90% of total GB electricity demand in 2030 if the weather patterns were the same as in the last 12 months. The government could not meet its target to make as much clean electricity as the grid uses over the course of a year even if we add in biomass generation as a ‘clean’ source.[2]

Absent the rapid growth of either hydrogen or gas power stations with CCS, we will also struggle to reach the second target of getting 95% of total electricity generation from clear sources. Put simply, clean energy is too variable to mean that 95% of generation will come from wind and other low carbon routes, even using the enhanced capacity of import interconnectors. At times of prolonged low wind, fossil electricity sources will often be needed throughout the year.

Achieving targets for 2030 generation.

The UK plans to increase its renewable energy capacity substantially by 2030. The plan is that ‘clean sources produce as much power as Great Britain consumes in total’ by this date. As a second objective, the government says, 95% of all generation should come from clean sources.[3]

In the basic analysis below, I suggest that neither target can be achieved unless wind and solar capacity is increased even more ambitiously than currently planned. Or that both of the Hinkley Point C reactors come online by 2030. At the moment EdF is expecting Hinkley Point C to start between 2029 and 2031.

I looked at half hour by half hour electricity generation data for the 12 month period from May 1st 2024 to April 30th 2025. I used data provided by NESO, the GB electricity system operator, to model what might happen in 2030 if the same meteorological conditions pertain.
NESO provides accurate estimates of the amount of electricity provided by the main sources of power for each thirty minute period. These sources include gas turbines, nuclear power stations, hydro-electric, solar, wind, biomass and other generators such as energy from waste plants.[4]
I assume that by 2030 the UK had reached the midpoint of the government’s targets. This means

o 46 gigawatts of solar, up from about 17.6 gigawatts in the year studied[5]

o 28 gigawatts of onshore wind, up from about 15.7 gigawatts in the year studied

o 46.5 gigawatts of offshore wind, up from about 15.0 gigawatts in the year studied

I multiplied the output of onshore wind, offshore wind and solar for each half hour in the year to the end of April 2025 by the targeted change in generating capacity. So, for example, if solar power delivered 1 gigawatt in a particular half hour period in this year I calculate that it would provide 2.6 gigawatts in 2030. 46 gigawatts of solar capacity in 2030 will provide 2.6 times as much electricity as 17.6 gigawatts does today.
I took note of EdF’s current intention to close two nuclear reactors in 2027. Hartlepool and Heysham 1 power stations have a maximum capacity of around 1,170 MW each. This leaves three reactors open in 2030: Sizewell B, Torness and Heysham 2 (although Torness and Heysham 2 are said to be closing during the course of 2030). I have optimistically forecast that nuclear power output will decline to about 60% of today’s levels in 2030, equivalent to a yearly average of around 3 GW of working capacity after allowing for outages and refuelling. I assume Hinkley Point C has not opened by 2030.

Over the 17,520 half hour periods of the year, output from wind and solar varies hugely. The highest wind output during the year was over a hundred times greater than the calmest period. These two events, over 22 gigawatts on 17th December 2024 and 0.2 gigawatts on 22nd January were just over a month apart. Of course these large differences will remain if we model an alternative world in which wind and solar capacities are much greater.

The results of the analysis

In the year under study to the end of April 2025, sources defined as ‘clean’ provided just under 48% of GB electricity supply.[6] These generating stations produced 134 terawatt hours out of a total of 282.5 terawatt hours consumed in GB.

The government targets an increase in solar power capacity from an average of about 17.6 gigawatts in the year studied to about 46 gigawatts in 2030.[7] This is a multiple of 2.6 times. Onshore wind is planned to go up from 15.7 to 28 gigawatts and onshore wind from 15.0 gigawatts to 46.5 gigawatts. NESO half hourly data does not separate onshore and offshore outputs so I have generated estimates of capacity factors from each source from information published elsewhere. The result is that expected output from wind will rise by about 2.55 times if new connections match the government’s target.

a. The basic test

Multiplying the power output from wind and solar in the 20224/2025 years as if the target 2030 capacities were already in use increases the amount of clean electricity produced to 278 terawatt hours.[8] Total electricity demand in the year under study was 282 terawatt hours.

Production of clean energy - 278 terawatt hours

Less Energy consumption - 282 terawatt hours

Surplus or deficit production - minus 4 terawatt hours

b. Increasing realism

Electricity production, after having falling regularly for several decades, will start increasing as EVs become more common, heat pumps gain in popularity and data centre use ramps up. So I increased total electricity consumption by 10% across all half hours in 2030.

The average output per megawatt of capacity from wind and solar power will also probably rise. Locations will be better chosen and technologies will improve. I propose a 4% increment in electricity production per unit of solar and wind power capacity in 2030. But nuclear production will fall as two nuclear plants are withdrawn from service in 2027, cutting average production by 40%. (I assume Hinkley Point C has not opened by 2030, an assumption which may be too harsh).

In addition, GB will probably have its first carbon capture and storage gas-fired power station by 2030 and I include an estimate of maximum output from this unit.

The impacts of these changes are as follows

Production of clean energy - 279 terawatt hours

Less Energy consumption - 311 terawatt hours

Surplus or deficit production - minus 32 terawatt hours

So under reasonable assumptions GB’s output of clean electricity will be only about 90% of the possible higher level of demand in 2030. Adding in biomass-based electricity production will not be sufficient to fill this gap, largely because of the much more limited subsidy available to Drax by 2030 and the restrictions placed on how much electricity is generated.

c. The government’s second objective – 95% of all production is clean

Why is the objective even more difficult to achieve? At those moments when wind and solar plus other clean sources are not sufficient to cover that hour’s demand, other sources will have to be brought into action. These may include more gas with CCS or hydrogen turbines but these source are unlikely to be operating at a large scale by 2030. The more variable is wind and solar output, the more other generators will have to be used, pushing down the percentage of clean production. This does not seem to be properly acknowledged in official communications.

In the 12 months of study, under the realistic assumptions including the 10% increase in demand and a 4% rise in wind and solar efficiency, GB would see about 6,400 half hour periods of excess production and about 11,100 half hours of deficiency. (This is before any biomass use is taken into account).

The excess production periods total 32 terawatt hours and deficiencies amount to about 71 terawatt hours. If the new gas with CCS power station operates during all the 11,100 half hours of deficiency, the volume of unfilled power need would fall to 66 terawatt hours when alternative generators or imports would have to be pulled into use. These numbers are in the context of total expected electricity usage of 311 terawatt hours so the UK would be unlikely to be able to make more than 80% of its electricity from clean domestic sources over the course of year.

Imports will help but even if clean imported electricity are available, the core problem is that periods of deficiency require more import connectors than are available. NESO predicts about 12 gigawatts of capacity by 2030, of which about 1 gigawatt represents the links to the island of Ireland and which are generally used to export from Great Britain, not import.[9]

Well over 25% of all half hour periods during the year under study experienced deficits of more than 11 gigawatts. Even in the highly unlikely event that all 11 gigawatts of import capacity were available at all these times, about 22 terawatt hours of demand would remain unsupplied. Other sources of electricity would have to be employed. At the improbable best, therefore, the UK could only hope to provide 94% of generation from clean sources, and this is assuming imports are all ‘clean’.

d. What about the impact of storage, such as using batteries?

The problem with using storage is that the demands for extra electricity, or alternatively the need to take in surplus power, typically cannot be met by the volumes of batteries proposed. If clean supplies are short and they persist for several days, batteries are almost useless. Long duration storage is needed rather than batteries, which are more capable of dealing with short term fluctuations in power supplies.

One particularly clear period under study was January 8 to January 11, when clean power, including gas with carbon capture, and 11 gigawatts of imports still left GB short of 1 terrawatt hour of power over a period of less than 3 days. The average deficiency during this period was about 15 gigawatts. NESO is estimating that GB will have a total storage capacity of about 50-99 gigawatt hours by 2030. So, at the very best, GB might have battery and pumped hydro storage of about 6 hours during a similar 65 hour period on 2030. The excess of demand over supply did not stop on January 11th. It went on for 360 hours in total up until 23rd January so batteries and other storage might have meet less than 2% of the eventual need.

What about periods of excess supply? The best days in the GB market were a month earlier from December 14th to December 24th. The average excess supply in this period was about 16 gigawatts, equating to about 6 hours of storage capacity rather than the 240 hours for which batteries would have been required to capture the excess. And even if other countries had wanted all that electricity, our export capacity would be routinely exceeded. The excess power would inevitably have been wasted.

Conclusions

GB will not attain clean power output levels equal its electricity demand in 2030. Assuming reasonable growth in electricity demand, improvements in solar and wind plus a more than 2.5 times volume of renewables capacity and a new CCS gas power station but declining nuclear output, clean power will only represent about 90% of national need.

The second target - ensuring that 95% of all generation will be clean – will not be met either. This is principally because when wind output is low the expected level of interconnection with Europe will not provide sufficient power to meet requirements. Even if 11 gigawatts of connectors are available, imports will frequently not fill the deficiency. So non-clean sources in GB, such as gas without CCS, will need to be utilised to match demand and supply.

Batteries are not particularly useful in helping to maximise the amount of clean power generation. Spells of low wind speed and little sun last far too long for storage systems to offer substantial aid, even if battery capacity rises as fast as expected.

To achieve its targets GB needs even more renewable capacity and an ability to turn surplus power into usable hydrogen that can be used to make electricity when supplies are tight.

[1] In reality, NZT may not operate much of the time because of low prices resulting from Europe-wide power surpluses at times of high wind speeds.

[2] However 2025 announcements of subsidy levels suggest that biomass will only probably produce about half as much electricity in 2030 as today.

[3] The Northern Irish electricity system is part of the all-Ireland network, separate from the GB system. The government’s targets refer to the GB network.

[4] The last coal-fired power station in GB closed during the twelve month period and is therefore included for part of the year.

[5] The figures used for the year under study are approximate average capacities across the 12 month period.

[6] Clean sources are defined as nuclear, wind, solar and hydro.

[7] The government offers a range for wind and solar capacity targets in 2030. I have chosen the mid point of this range.

[8] Wind, solar, nuclear and hydro.

[9] https://www.neso.energy/document/346651/download