Denmark’s Grid Runs Out of Room

There are days on the North Sea when the weather gives you nothing. The sky sits low and grey, the air barely moves, and the turbines that usually define the horizon become still furniture. The Danes have a word for it, dunkelflaute, meaning a spell when wind and solar output fall together across a wide area. Ireland, with its own faith in wind and interconnectors, should understand the problem without much translation.

For Denmark, the issue is sharper because much of the old domestic backup generation has already been retired. When the calm comes, the Danish grid has to pull electricity through undersea cables from Sweden, Norway and Germany (Politiken). In 2025, Denmark imported more electricity from its neighbours than in any year before (Portfolio.hu). That is testing a larger European bet: that cross-border cables can take the place of power stations countries are closing down.

Denmark's grid is running out of room

Weather is only the first difficulty. Energinet, the Danish grid operator, says data centres, hydrogen plants and battery projects have applied for grid connections totalling about 60 GW, roughly eight times Denmark's current peak demand (Energinet). A good deal of that is speculative. Companies file early, and many projects never leave the page. But even a modest share would put pressure on a grid that is already struggling to keep pace. Energinet has stopped accepting new transmission-level connection requests.

District heating shows the strain from the demand side. About one in four Danish district-heating companies say grid connections have been delayed or that they received less capacity than they asked for. Dansk Fjernvarme, the industry group, expects electricity's share of district heating to rise from about 10% today to 45% by 2035 (Via Ritzau). The story is simple enough: more demand, fewer domestic plants, and a grid with little room left.

Who sells power, who pays for it

Europe's electricity market sends power from cheaper regions to dearer ones through cross-border cables until those cables are full (European Commission). It works well when the shortage is local. It works less well when the same weather system leaves everyone short.

France shows the advantage of keeping generation that can be switched on. In the first half of 2026, France exported a net 51 TWh, earning producers about €3 billion and generating roughly €1.3 billion in cable-usage revenue for RTE, the French grid operator (Le Figaro). France sold at an average price of about €61.9/MWh. Importing countries paid almost twice that, around €111.6/MWh (Les Énergies Renouvelables). Nuclear power gives France electricity on demand, and that becomes a paying asset when neighbours are tight.

That does not make French electricity cheap for everyone at home. Household tariffs will rise 2.5% on 1 August for about 19.37 million households (Challenges). Grids and backup capacity have to be paid for whatever the wholesale price is doing. In the same six months, French wholesale markets recorded 407 hours of negative prices, periods when surplus electricity had nowhere profitable to go, while the infrastructure bill kept rising.

Sweden shows a different division of winners and losers. Its grid is split into pricing zones, so southern regions closest to Denmark face higher wholesale costs when Danish demand draws power across the border (GP). Swedish generators can profit by selling into a tight Danish market. Swedish households in those same zones pay more. The Danish island of Bornholm has only 35 MW of guaranteed import capacity from Sweden, well below the cable's technical limit, because pressure on southern Swedish grids limits what can be promised (Bornholm.nu).

Germany is buying insurance of its own. The Bundesnetzagentur, Germany's energy regulator, has 7,407 MW of grid reserve for winter 2026/27: plants kept outside the normal market and used only in emergencies (Bundesnetzagentur). Berlin passed a capacity-market law in May 2026 that will pay plants and batteries to be available even when they rarely run. That is the backup Denmark chose not to keep.

Finland points to the physical risk. When one of its two undersea links to Estonia went offline for repairs, prices rose and supply tightened immediately (Grivolt). A cable can be congested, under maintenance, or simply unavailable at the wrong moment.

ENTSO-E, the body coordinating Europe's grid operators, runs continent-wide checks on whether countries will have enough power in stressed periods, because cross-border help is conditional rather than automatic (ENTSO-E, ACER). Denmark exposes the bargain beneath Europe's greener grid. Cables lower costs when conditions are normal. They do not guarantee electricity when the wind drops across a whole region. The countries that kept plants they can switch on will have pricing power. The countries that trusted the cables may find the hardest hours are also the dearest.