Powergen's executive director of UK operations, Nick Baldwin, said: "We are confident that the Blyth project will demonstrate the robustness of the technology and lead to the further harnessing of the UK's substantial offshore wind asset."
The two turbines are the largest of their kind to be erected anywhere in the world. They have the capacity to power 6,000 average households.
The UK is the windiest place in Europe and, theoretically, has enough offshore wind to supply three times its current electricity requirements.
The turbines were officially opened on Thursday by energy minister Helen Liddell.
They stand in six metres (20ft) of water in the North Sea.
'Wind asset'
The scheme was developed by a consortium of four companies: Border Wind, PowerGen Renewables, Nuon UK and Shell Renewables.
Powergen's executive director of UK operations, Nick Baldwin, said: "We are confident that the Blyth project will demonstrate the robustness of the technology and lead to the further harnessing of the UK's substantial
offshore wind asset."
The £4m project will be monitored and evaluated as part of the Department of Trade and Industry's Wind Energy Programme.
Britain is under an EU obligation to meet 10% of its energy needs from renewable resources, including wind, by 2010.