Natural gas and electricity markets were already surging in Europe when a fresh catalyst emerged: The wind in the stormy North Sea stopped blowing.

The sudden slowdown in wind-driven electricity production off the coast of the U.K. in recent weeks whipsawed through regional energy markets. Gas and coal-fired electricity plants were called in to make up the shortfall from wind.

Natural-gas prices, already boosted by the pandemic recovery and a lack of fuel in storage caverns and tanks, hit all-time highs. Thermal coal, long shunned for its carbon emissions, has emerged from a long price slump as utilities are forced to turn on backup power sources.

The episode underscored the precarious state the region’s energy markets face heading into the long European winter. The electricity price shock was most acute in the U.K., which has leaned on wind farms to eradicate net carbon emissions by 2050. Prices for carbon credits, which electricity producers need to burn fossil fuels, are at records, too.

Wholesale day-ahead power prices since 2019Source: ICISNote: €1 = $1.18
2020’21-50050100150200250300€350a megawatt-hourGermanyU.K.

“It took a lot of people by surprise,” said Stefan Konstantinov, senior energy economist at data firm ICIS, of the leap in power prices. “If this were to happen in winter when we’ve got significantly higher demand, then that presents a real issue for system stability.”

Prices for power to be dispatched the next day rocketed to £285 a megawatt hour in the U.K. when wind speeds dropped last week, according to ICIS. That is equivalent to $395 a megawatt hour and marked a record on figures going back to 1999.

In electricity markets, the cost of generation at the most expensive supplier determines prices for everyone. That means that when countries derive power from thermal plants with comparatively high running costs, it boosts prices for the whole market. Operating costs at fossil-fuel power plants are high right now after a relentless climb in prices for gas, coal and carbon permits.

Energy prices could shoot even higher if cool temperatures stop gas stores replenishing before the period of peak winter demand, said Tom Lord, a carbon trader at U.K.-based Redshaw Advisors. “You’ve got a gas market that’s extremely tight,” he said.

Electricity, gas, coal and carbon markets have a way of feeding on one another. High gas prices prompted utilities to burn more coal, so they had to buy more emissions allowances. Expensive carbon permits then prodded energy companies to turn back to gas, whose price rose again because the fuel is in short supply.

The feedback loop has the potential to ripple into the broader economy. European Central Bank President Christine Lagarde this month referred to energy markets as one of the main forces driving inflation higher.