UK nuclear generation fell to its lowest level since the 1980s last year, forcing greater reliance on gas even as renewable output reached another record.
Official DESNZ figures show nuclear generation dropped 12% in 2025 to 35.9TWh because of refuelling, planned maintenance and unplanned outages across the ageing fleet. The decline helped push the low-carbon share of electricity generation down slightly to 64.3%.
The fall comes at a difficult time for Britain’s power system.
Electricity demand increased 1.2% to 323TWh while the Government is preparing for much sharper growth from electric heating, transport, industrial electrification and data centres.
New nuclear projects are not expected to arrive quickly enough to replace all the output lost as older stations close. That creates a growing gap between the existing fleet and future projects including Hinkley Point C, Sizewell C and planned small modular reactors.
Gas-fired generation rose 6.6% to 93.2TWh, accounting for 31.8% of all UK electricity generation. The increase shows how gas continues to provide backup when nuclear output is weak, renewable generation falls or demand rises.
Total fossil fuel generation increased 4.1% to 94.9TWh despite record renewable output.
That dependence will complicate the Clean Power 2030 target, particularly during periods of low wind and high demand.
Half our power is renewable
Renewable generation rose 5.9% to a record 153TWh and supplied 52.1% of UK electricity. It was only the second year in the published series that renewables provided more than half of generation.
Wind remained the largest source at 86.4TWh while bioenergy reached 41TWh. Solar recorded the strongest growth, jumping 34.2% to a record 20.1TWh. The surge reflects both rising installed capacity and unusually sunny conditions, although the figures underline solar’s growing role in the electricity mix.
Its seasonal and weather-dependent output also strengthens the case for more storage, flexible demand and network investment.
The UK also completed its first full year without coal-fired electricity generation following the closure of Ratcliffe-on-Soar in September 2024.
Oil-fired generation fell 2.5% to 1.7TWh.
While coal has disappeared from the system, the rise in gas shows Britain has not yet removed fossil fuels from electricity generation.
Shifting energy use
Industrial electricity consumption fell 2% to 76.7TWh, its lowest level since 1983 and the fourth consecutive annual decline.
DESNZ attributes part of the longer-term reduction to energy efficiency and the shift from traditional manufacturing towards higher-value sectors. However, the continued fall will also raise questions over whether lower industrial demand reflects efficiency or further evidence of deindustrialisation.
Domestic electricity consumption increased 2.6% while commercial demand rose 1.5%. Overall demand remains below 2019 levels but the direction has begun to change.
Data centres are becoming an increasingly important part of that picture. DESNZ estimates they consumed 4.5TWh of grid electricity in 2024, up from 1.3TWh in 2020.
That represents an increase of 246% in four years and helps explain Ofgem’s concern in the surge in speculative data centre connection applications.
Energy Imports up
Electricity trading with neighbouring countries also reached new highs.
Gross imports rose to a record 43.9TWh while exports increased 38% to 14.2TWh, the second-highest level recorded. Net imports fell 11% to 29.7TWh, with France supplying 21.9TWh and Norway 9TWh on a net basis.
Total UK electricity generation rose 2.6% to 293.6TWh but remained below demand, leaving interconnectors central to balancing the system.
The 2025 figures show a power sector moving in two directions at once.
Renewables are breaking records and coal has disappeared but falling nuclear output, rising gas generation and growing demand expose the challenge Britain faces before enough new firm low-carbon capacity comes online.
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