Denmark's 2015 Wind Record: 140% of Power Demand Explained

Denmark’s Wind Farms Met 140% of Its Power Demand for a Day in 2015

NOVA PBS / YouTube

Yes, it happened. On the evening of Thursday 9 July 2015, strong winds let Denmark's wind farms generate 116% of the country's electricity demand. In the early hours of Friday, when demand dropped overnight, output passed 140% of what Danes were using. The surplus flowed through interconnectors to Germany, Norway and Sweden. It was a one-day record, not a permanent state, but it showed how far a small country had pushed wind power.

What happened on 9 and 10 July 2015

A windy summer evening combined with modest demand gave Danish turbines an unusual opportunity. According to figures from Energinet.dk, the national transmission system operator, wind production rose above total domestic consumption on Thursday evening and peaked at more than 140% of demand around 3 a.m. on Friday.

The Guardian, which reported the record at the time, said that most of the excess, roughly 80%, was split between Germany and Norway, with the remaining fifth going to Sweden. Norway in particular is a useful partner: its large hydropower reservoirs can hold back water when imported wind power is cheap and release it later when it is needed.

Oliver Joy, a spokesman for the European Wind Energy Association at the time, told the paper the record showed "that a world powered 100% by renewable energy is no fantasy". He added that Europe would need better grids and more cross-border trading to repeat it on a continental scale.

Energinet.dk

The snapshot above, published by Energinet, shows the state of the grid at one moment that evening, with wind turbines producing far more than the country was consuming and power flowing out over the borders. Energinet publishes such data live, which is why the record could be confirmed within hours.

What "140%" really means, and what it does not

Headlines about Denmark "producing 140% of its electricity needs" are accurate for a few hours, but they are easy to misread. A few points help put it in context:

It was a peak, not an average. The 140% figure came in the middle of the night, when demand is lowest. Over the whole of 2015, wind supplied about 42% of Denmark's electricity consumption, itself a national record at the time.
Denmark is small and well connected. With under six million people and strong links to its neighbours, it can export surplus power and import when the wind drops. Few countries can lean on Norwegian and Swedish hydropower in the same way.
Other power plants still mattered. Combined heat and power stations, imports and, increasingly, biomass kept the lights on during calm spells. A few weeks later, on 2 September 2015, West Denmark ran for 24 hours without any of its central power stations, another milestone in the same direction.
It was not the first spike. On 21 December 2013, wind had already met 102% of demand over a day and 135% for one hour.

How Denmark became a wind power leader

Denmark's lead goes back decades. After the oil crises of the 1970s, the country, which had little oil or gas of its own at the time, started looking for homegrown energy. Small Danish manufacturers and farming cooperatives built some of the first modern commercial turbines, and local ownership helped win public support. Companies that grew from that early industry, such as Vestas, are still among the world's largest turbine makers.

By the end of 2015 Denmark had about 5,070 MW of wind capacity installed. Most of it was onshore, often in rows along farmland and coasts, while large offshore parks such as Horns Rev in the North Sea added more. Steady political backing, long-term targets and a grid operator able to balance a variable supply all played a part.

Did the predictions come true?

In 2015 Kees van der Leun of the Ecofys energy consultancy predicted that Denmark could get around half of its electricity from renewables by 2020. Wind alone came close to that and then went further. According to figures compiled on Wikipedia from Danish energy statistics, wind turbines produced more than half of Denmark's domestic electricity output in 2019 and 2020, and around 58% in 2023, one of the highest shares in the world.

Capacity kept growing, reaching about 7,500 MW by 2023, of which roughly 4,900 MW was onshore and 2,650 MW offshore. New offshore farms and links such as the Kriegers Flak interconnector with Germany were added to move that power around the region.

The contrast with Britain in 2015

The Danish record arrived just as the UK went the other way. In 2015 David Cameron's government announced an early end to subsidies for new onshore wind farms and tightened planning rules, which made onshore projects in England very hard to build. The British wind industry, the Guardian noted, looked at Denmark with some envy. Offshore wind continued to grow quickly in UK waters, and the restrictions on onshore turbines in England were relaxed again in 2024.

Why the record still matters

A single windy night does not prove that any country can run on wind alone. What it did show, in 2015, was that a modern grid could absorb very large amounts of variable renewable power, share it with neighbours and stay stable. The lessons Denmark learned, about interconnectors, flexible demand, storage in neighbours' hydropower and accurate forecasting, are now central to energy plans across Europe.

The practical takeaway is that the question has shifted. It is no longer whether wind can provide a large share of electricity, but how quickly grids, storage and cross-border links can be built to use it well.

Sources: Wikipedia: Wind power in Denmark; The Guardian, 10 July 2015; data from Energinet.dk; animation via NOVA PBS on YouTube; originally reported by True Activist.

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