(Bloomberg) -- A trading error by Centrica Plc’s Nordic arm may have contributed to power prices plunging so low that some homes in the region will get free electricity at times on Wednesday. 

The UK utility erroneously didn’t buy enough supplies in an auction on Nord Pool AS, which indicated to the market that demand was extra low at a time when wind power output was surging. 

Centrica’s mistake comes just months after a Norwegian company sent shockwaves through the market with incorrect bidding that also sent power prices below zero in Finland. When prices turn negative, some consumers with contracts tracking the wholesale market will benefit as they don’t have to pay anything for their electricity. 

Read: Trader Error Means Some Finnish Consumers to Get Free Power

Day-ahead power prices slumped to €1.30 ($1.41) per megawatt-hour in Sweden and Finland, with as many as 13 individual hours showing negative levels, according to Nord Pool data. 

Centrica said in a market message that it faced a shortfall of about 600 megawatts on average during Wednesday, adding that it would be looking to “unwind this position before delivery to balance the portfolio.” The utility didn’t respond to requests for comment.  

At the same time, wind power output across the region surged to more than 25 gigawatts on Wednesday morning, compared with just above 5 gigawatts on Tuesday, according to grid data. 

The low prices are also impacting the region’s nuclear plants, with Swedish utility Vattenfall AB curbing output at its Forsmark plant north of Stockholm. It’s three reactors at the site were all operating below 70% on Wednesday morning.

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