The ESB is taking a 50% stake in an offshore wind farm project in Scotland.
Construction of 450 megawatt Neart na Gaoithe project is underway, and expected to be complete in 2023.
It is being led by French firm EDF Renewables.
It is understood the cost of such a stake would be around €1.5m per megawatt - costing some €337m.
The ESB says the stake is "a significant milestone" in its plans for a low carbon portfolio of scale.
The wind farm will offset over 400,000 tonnes of carbon emissions each year.
Twenty-five banks are lending money to fund the wind farm, which will supply enough electricity for around 375,000 homes.
Pat O'Doherty is chief executive of the ESB: "Our 50% stake in Neart na Gaoithe fits entirely with ESB's Brighter Future strategy to build a balanced low carbon generation portfolio of scale.
"Offshore wind is one of the main technologies underpinning the clean electricity systems that will power our societies into the future.
"This investment in the Neart na Gaoithe project builds on significant ESB involvement in offshore wind off the Irish coast as ESB develops its experience to assist Ireland deliver its Climate Action Plan".
The chief executive of EDF Renewables, Matthieu Hue, adds: "This is a hugely important step for the project and we are excited to get work underway with our equity partner ESB and all of our contractors.
"The wind farm will play an important role in de-carbonising the UK electricity system to reach the country's net zero targets.
"It is evidence of our continuing investment and growth in Scotland and it shows the ability of EDF in the UK to provide diverse solutions for electricity consumers in terms of low cost renewable electricity."
Neart na Gaoithe, which means 'strength of the wind', will have 54 turbines and be located off the east coast of Scotland.