Claim: "Renewables are not the solution - because sun and wind are intermittent"
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It's a fair question, and the people who run and plan our electricity system take it seriously. But variability is a known engineering problem with known solutions. It is not a reason to slow down.
Renewables already generated more than half of UK electricity in 2025, and the lights stayed on. A reliable, mostly-renewable system works by combining several things at once: a diverse mix of sources that peak at different times; stronger links to our neighbours; storage that covers everything from minutes to whole seasons; demand that can shift to when power is plentiful; and a society prepared to ease demand during the very rare, longest calm spells.
The Royal Society has found that Britain's electricity needs could be met by wind and solar backed by large-scale storage, at a cost that compares well with other low-carbon options. Independent studies consistently find that a fast shift to clean energy is cheaper than staying on fossil fuels - and the faster we go, the more we save.
These developments now demonstrate that the greater risk to reliability and to energy price spikes is to delay the transition.
With thanks to Professor Benjamin Sovacool for his help with this question.
More Detail
1. The concern is real – and it’s already being planned for
Wind and solar output varies over seconds, days, seasons and even decades. However much capacity we build, there will be cold, still, grey winter spells when output is very low (sometimes called a dunkelflaute, or “dark doldrums”).
That is exactly why serious planning doesn’t rely on average output. The Royal Society’s 2023 study modelled Britain’s system hour by hour using 37 years of real weather data, including the worst calm periods on record, and sized storage to cover them.
2. Where we are now
Renewables generated a record 52.5% of UK electricity in 2025 – the second year running above half.
Wind alone supplied around 30%, the largest single renewable source.
Britain ended coal power in 2024.
Gas still provided roughly 31%. The task now is to replace the role gas plays in balancing the system – not to prove that renewables can run a grid. They already do much of the time.
3. How a renewables-based grid keeps the lights on
No single technology solves variability. Together, these do:
A diverse mix. Wind is strongest in winter; solar in summer. Offshore wind spread across the North Sea, Irish Sea and Atlantic coast is very unlikely to be calm everywhere at once. Tidal power is entirely predictable, years in advance. Hydro and wave add further variety, and the latest deep-drilling technology from the oil industry means geothermal can now provide round-the-clock clean energy almost anywhere. The UK has some of the best wind, wave and tidal resources in Europe.
Connecting to neighbours. Weather systems rarely becalm the whole of Europe simultaneously. Interconnectors let Britain import when it’s still here and windy elsewhere, and export when we have a surplus. But we need much greater capacity.
Storage across every timescale.
Minutes to hours: batteries – grid-scale, in homes, and increasingly in electric cars.
Hours to days: pumped hydro, compressed or liquid air.
Weeks to seasons: green hydrogen made from surplus renewable power and stored underground in salt caverns. The UK has stored hydrogen in salt caverns since 1972, and the British Geological Survey has identified ample suitable geology in Cheshire, Wessex and East Yorkshire.
Flexible demand. Much of tomorrow’s demand can move in time: electric vehicles charging overnight or when it’s windy, heat pumps paired with heat storage, smart tariffs, and industrial users. Price signals do the work.
Using less energy in the first place. Insulation, efficient heating and better-designed transport cut the amount of supply and storage needed. Research by the Centre for Research into Energy Demand Solutions (CREDS) shows the UK could roughly halve its energy use while maintaining or improving quality of life.
Rare extremes: storage plus a prepared society. Long-duration storage can be sized to ride through the worst calm, dark spells in decades of weather records. On top of that, a prepared society can respond to a rare dunkelflaute, much as we already adapt to heavy snow. These spells are forecast days in advance, so households and businesses can be asked to ease demand for a few days: working from home and avoiding unnecessary car journeys, delaying EV charging and other flexible use, and paying industry to pause energy-intensive processes. Britain’s grid operator already pays households and businesses to cut use at peak times. This is far cheaper than keeping a fleet of power stations idle for the handful of days they might be needed.
4. What does it cost?
Royal Society (2023): backing wind and solar with storage compares very favourably on cost with other low-carbon alternatives, and offers greater energy security. A portfolio of storage types could lower costs further.
University of Oxford (2022, Joule): a fast transition to clean energy would save the world at least $12 trillion compared with continuing to rely on fossil fuels – because renewable, battery and electrolyser costs keep falling, while fossil fuel costs don’t. It also found that the faster the transition, the bigger the savings.
Stanford University (2022): grid modelling for 145 countries found 100% wind, water and solar, plus storage, could match demand every hour, cut annual energy costs by around 60%, and pay back the investment in about six years.
Climate Change Committee (2025): the CCC’s Seventh Carbon Budget includes detailed modelling of the pathway to decarbonising the UK economy. It forecasts that after an outlay of £319 billion, the entire net zero project becomes cash positive, and by 2050 the UK will be saving around £35 billion every year – though 2050 is of course too slow.
A note on timelines: many of these studies were framed around the UK’s 2050 net zero date, because that was the policy goal when they were written. They prove the case that a reliable, affordable renewables-based system is achievable. But the science has moved on: the climate and nature crisis is accelerating, and we now need to go much faster. The evidence suggests that going faster also saves more money.
The common thread: clean energy needs more investment upfront and much less spending on fuel afterwards. Wind and sunshine don’t send a bill.
5. This isn’t a fringe view
A 2022 review of the whole field of 100% renewable energy research, led by LUT University with Oxford Brookes and others (Institute of Electrical and Electronics Engineers), found broad agreement across independent studies that highly renewable energy systems are technically feasible and economically viable, worldwide and at national level.
6. What would make the difference
The Royal Society warned that long-duration storage has been seriously underestimated and that construction of large-scale hydrogen stores needs to start soon to be ready in time. The practical priorities are:
Business models and market rules that make long-duration storage investable.
Faster grid connections and network build-out.
More interconnection with Europe.
Smart, flexible demand as the default for EVs and heat pumps.
A serious national programme on insulation and energy efficiency.
These are policy choices well within Parliament’s reach.
Key sources
Royal Society (2023), Large-scale electricity storage
Way, Ives, Mealy & Farmer (2022), Empirically grounded technology forecasts and the energy transition, Joule – University of Oxford summary
Breyer et al. (2022), On the History and Future of 100% Renewable Energy Systems Research, IEEE Access
Jacobson et al. (2022), Low-cost solutions to global warming, air pollution, and energy insecurity for 145 countries, Energy & Environmental Science
Climate Change Committee (2025), The Seventh Carbon Budget
DESNZ (2026), Energy Trends: UK electricity generation in 2025
CREDS, The role of energy demand reduction in achieving net-zero in the UK
