Cross-border power cables meet the limits of political consent

On a Thursday morning in August, with a heat dome parked over northern Europe and wind turbines barely spinning, Britain was drawing a fifth of its electricity from undersea cables to the continent. French nuclear plants alone delivered 3.54 gigawatts, covering 11 per cent of British demand. That was more than twice the output of every wind farm in the United Kingdom combined at that hour.

The figures illustrate a dependency that has crept up over a decade of interconnector construction. Britain now has seven high-voltage links to France, the Netherlands, Belgium, Denmark and Norway. Over the course of a full year, the country imports roughly a tenth of its electricity this way. On days when domestic generation falters, the share climbs sharply. The economic logic is sound: French nuclear power is frequently cheaper than running British gas plants, and on breezy, sunny days the flow reverses, letting Britain sell its surplus renewable output abroad.

A summer of strain on the system

The summer of 2026 has tested that logic repeatedly. A succession of heatwaves drove up air conditioning demand while simultaneously reducing the efficiency of gas turbines and making it harder to cool French nuclear reactors. Some generation capacity was offline for routine maintenance ahead of winter. Low wind added to the squeeze. The result has been a series of days when Britain leaned heavily on imports, and when the body responsible for keeping the lights on took steps that rattled neighbouring grids.

On 23 June, the National Energy System Operator, Neso, cut off exports to the Netherlands at short notice. The British grid had been operating below its preferred frequency limits for almost two hours, though not in breach of statutory requirements. An investigation into what happened that evening is still under way.

Then in July, Neso went further. The operator instructed wholesale market traders not to export power through four interconnectors during several hours in the day-ahead market, a move designed to ensure Britain retained enough electricity for its own needs. The intervention was reported by the Financial Times and drew sharp reactions from continental operators who depend on predictable flows.

Phil Hewitt, a director at the energy market specialist Montel, puts the continental perspective bluntly: "The impact of Neso redispatching interconnectors close to real time can cause trouble, especially for smaller markets like Belgium and the Netherlands." The concern is not abstract. Belgium and the Netherlands have smaller grids that are more vulnerable to sudden changes in power direction on cross-border cables.

Tighter rules after the disruptions

In response to the summer's disruptions, the contractual framework governing six of Britain's interconnectors was tightened in May. Late changes to the direction of power flow on each cable, those connecting Britain with Belgium, Denmark, France and the Netherlands, are now limited to 300 megawatts per link. The restriction is designed to prevent a repeat of the sudden reversals that left neighbouring markets scrambling.

Peter Atherton, an independent energy analyst, offers a candid view of how Britain is perceived across the Channel: "The UK is potentially seen as the weak link in the European system." A country that imports heavily, then abruptly curtails exports when its own grid comes under pressure, is a neighbour that continental operators may come to regard as unreliable.

Norway turns against new cables

Britain is not alone in facing political friction over cross-border electricity. Norway, whose vast hydroelectric capacity makes it a natural power exporter, has effectively called a halt to new interconnector projects after a consumer backlash over domestic electricity prices. Norwegian voters blamed existing cables for linking their prices to higher continental markets, pushing up bills at home.

In 2023, Oslo scrapped plans for a second 1.4-gigawatt cable to Peterhead in Scotland, which would have replicated the capacity of the existing North Sea Link. The decision sent a clear signal: cheap Norwegian hydro will no longer be treated as an inexhaustible resource for European neighbours. Mainstream parties in both Norway and Sweden have grown cooler towards building additional links, reflecting a shift in public opinion that cuts across the usual political divides.

The Norwegian case illustrates a broader tension. The economics of interconnection assume that power flows to wherever it commands the highest price, smoothing out differences across markets. But voters in exporting countries see their bills rising to match demand in importing countries, and they object. As the International Energy Agency has documented, electricity market coupling across Europe was designed to deliver efficiency gains, not to redistribute costs from high-price to low-price countries. The political reaction in Oslo suggests the design may need rethinking.

The Le Pen variable

An even larger risk is taking shape in France, though it has received remarkably little attention in Britain. Marine Le Pen, currently leading the polls ahead of next year's French presidential election, has pledged to pull France out of the European Union's cross-border electricity arrangement, a system that is closely integrated with Britain's own market. Her National Rally party argues that French consumers would pay less if the country stopped exporting so much of its nuclear output.

French energy companies are alarmed by the proposal. They regard it as economically self-defeating and a threat to the stability of the continental grid. But the political appeal is obvious: France has the cheapest electricity in western Europe thanks to its nuclear fleet, and the promise of keeping more of that cheap power at home is a potent electoral message.

Hewitt is clear about the consequences for Britain. "There would be price rises for UK consumers and questions for security of supply if the National Rally gets in in France and implements their policy," he says. He adds that the trend extends beyond France: "Mainstream parties in Norway and Sweden are increasingly anti building more interconnectors, they're saying 'enough is enough'. If there is no more build-out and France says 'we're not going to send you any of our electricity', the position looks more dicey." He concedes this is "an edge case" but insists "political risk is there. Populism can cause trouble."

Why Paris and Oslo matter disproportionately

Not all interconnectors carry the same strategic weight. The French and Norwegian cables are the ones that consistently supply cheap power to Britain. The links to Belgium, Denmark and the Netherlands see more two-way traffic, with flows reversing depending on market conditions. If either France or Norway decided to curtail exports, the effect on British supply would be immediate and significant. The other cables could not compensate.

This asymmetry matters because Neso cannot control the politics at the far end of a subsea cable. The operator's mandate is to keep the British grid stable, and this summer it has done so, albeit at considerable cost. Gas-fired generators were paid high prices to fire up during the solar eclipse and on low-wind days. Interconnector imports were expensive too. But the system held. The question is whether it can hold if the political framework that underpins it begins to fracture.

The democratic reality behind energy nationalism

Atherton states the underlying dynamic without embellishment: "It is a fundamental fact of democratic life that no country will export power if it means potential blackouts in its own cities. It would be electoral suicide, whatever contracts you have in place." This is the core challenge for cross-border electricity markets. Contracts and regulations can specify who has the right to buy power and at what price. They cannot override a government that decides its own citizens come first.

The trend is not confined to Europe. Energy nationalism has surfaced in countries as different as Indonesia, which has restricted nickel exports to favour domestic processing, and India, which has imposed tariffs on wheat shipments. In each case, the logic is the same: domestic voters expect their government to prioritise their access to essential resources. Electricity is no different, and the more visible interconnector cables become as a source of imported power, the more politically exposed they become.

Europe's grids have grown more complex as renewable generation has expanded. Supply is decentralised. Intraday price swings are more extreme. Balancing supply and demand is harder than it was when a handful of large thermal plants could be dispatched at will. Interconnectors were supposed to manage that complexity by allowing surplus power in one country to fill shortages in another. In principle they still do. In practice, the political assumptions behind them are under strain.

A better balance, years away

The medium-term outlook offers some relief. Britain is expected to add substantial renewable capacity and new nuclear generation over the next decade. Sometime in the 2030s, the country should switch from being a net importer to a net exporter of electricity, according to Office for National Statistics energy data and government projections. That transition would reduce the strategic vulnerability that the summer of 2026 has exposed.

The shorter term is another matter. Between now and the early 2030s, Britain remains dependent on the willingness of its neighbours to keep sending power across the Channel and the North Sea. Each summer of extreme heat and low wind will test that willingness. Each political shift in Oslo or Paris will reshape the calculation.

For now, pan-European electricity cooperation still functions. Cables carry current. Markets clear. But the events of this summer have revealed how quickly operational stress can turn into diplomatic friction, and how easily energy nationalism can override the assumptions built into cross-border contracts. Managing a solar eclipse, as Neso did without incident, is straightforward by comparison.