Last week energy records were broken: not in the price of oil and gas but in the generation of wind power. At Wednesday lunchtime, between 1.30 and 2pm, turbines were cranking out 24 gigawatts of clean energy. For a moment Ed Miliband’s utopian energy vision was realised: 55 per cent of our electricity was being generated by wind, a further 22 per cent by solar and 10 per cent by nuclear. Just 2 per cent came from fossil fuels. The wholesale cost was only £4.81 per megawatt hour.
Yet look at what happened 11 weeks earlier. On the evening of January 5 the price paid to generating companies climbed to £477/MWh. A few days later gas was producing two thirds of all electricity, with wind and solar production reduced to a mere 2GW.
Scarce wind and no sunlight — a state of affairs known by the haunting German name Dunkelflaute, meaning “dark calm” — is National Grid’s new worst nightmare. It is the most blindingly obvious problem with renewable energy, and yet we have found ourselves painfully exposed to it. After the final coal power stations were switched off in 2024, last winter was the first with gas as our only flexible source of electricity. On January 8, 2024, at teatime, a Dunkelflaute caused wholesale electricity prices to spike to £2,900/MWh.
The reason for these high prices is that Britain’s electricity generation system will use up whatever renewables it has available first and then turn to gas. When our own power stations cannot meet supply, the grid must turn to expensive imports.
Britain’s expansion of renewable energy has been nothing short of remarkable. Capacity was about 5GW in 2010; today it is more than 30GW. It is, theoretically, cheap. It is also a nightmare to manage.
Britain has an average electricity demand of 33GW and capacity close to 40GW. By 2035, according to the Royal Meteorological Society (RMetS), our typical electricity demand — boosted by a projected rise in the use of electric cars and heat pumps and the growth of data centres — will have risen to 52GW. By then our wind and solar capacity will be somewhere in the region of 150GW. Three times as high! But this spare capacity remains completely useless against the Dunkelflaute.
Let us examine this problem a bit more closely. The RMetS looked at the weather during that cold, still month in January 2025 and explored how our 2035 energy grid would fare in such conditions. For parts of the month wind would generate too much electricity. At other times it would generate almost nothing. The same is largely true under a 2050 system, to a more extreme extent: there will be January days when Britain produces nearly twice as much electricity as is needed, and days when renewables produce virtually zilch.
Nuclear power is the obvious choice to bridge the gap. But our capacity, 6.5GW, will actually fall in 2028 when Hartlepool and Heysham 1 close. Even in 2034 we will have less nuclear capacity than now. In the meantime there is energy storage — we have a smattering of pumped hydroelectric storage, and the government is betting big on batteries by 2030 — but even those are not much help in a long Dunkelflaute.
But there are problems on windy days too. Electricity cannot be beamed to where it is needed, so we pay wind turbines to switch off and pay gas turbines to make power instead. The sum of these “balancing payments” reached £2.7 billion last year and meant wind output was 13 per cent less than it could have been.
The cause is historical: when Britain’s national grid was built in the 1920s and 1930s, it was designed to connect coal power stations with power-guzzling urban centres. In the renewable age the centre of energy gravity has shifted to the north: to Scotland and offshore turbines in the east. So Britain is being rewired, at a cost of £70 billion over the next few years. Energy superhighways are being built that will carry power from Scotland to England, and from east to west. But many projects won’t come online until about 2034.
And all of this is expensive. Modelling by the energy analyst Ben James suggests that even if wind gives us cheaper wholesale electricity than today, the average bill in 2030 will be £1,045 — about £80 more, including inflation. Much of that difference is network costs: the cost of transmitting electricity from one end of Britain to another and distributing it to households, but also of paying wind turbines to stop spinning and gas turbines to fire up, are all about to soar.
Wind and solar are the cheapest sources of electricity we have. Building a network that can carry them — and contingencies for when it is dark and still — is anything but. Until the grid catches up with our rush towards wind, British households will pay a premium.