Some 1.2MW, enough electricity to power 1,000 homes, has been produced by SeaGen, at the mouth of Strangford Lough.
This equates to the highest level of power produced globally by a tidal stream system and could be a guide of what the future holds in the renewable energy industry.
The company behind the SeaGen tidal energy convertor is Marine Current Turbines.
The firm’s managing director, Martin Wright, said: “This is the highest power so far produced by a tidal stream system anywhere in the world and exceeds the previous highest output.
“Generating at full power is an important milestone for the company and in particular our in-house engineering team.
“It demonstrates, for the first time, the commercial potential of tidal energy as a viable alternative source of renewable energy.”
The Carbon Trust is attempting to improve research into marine energy by investing £1m (Euro 1.07m) to transfer established engineering systems for use in marine generators.