The acquisition of ConnectGen from Quantum Capital is part of the Spanish company's pivot from oil and gas to renewables, with a special focus on the United States.
The move "accelerates our commitment to renewable generation in one of the markets with the greatest potential for future growth," Repsol Chief Executive Josu Jon Imaz said in a statement on Thursday.
Repsol's purchase comes a day after it agreed to sell its oil and gas assets in Canada to Peyto (PEY.TO) for $468 million.
ConnectGen's 20 GW in planned onshore wind, solar and energy storage projects will help Repsol achieve its goal of reaching 20 GW of installed renewables capacity by the end of the decade.
It currently has around 2 GW of renewables in operations and another 3 GW under construction.
This is Repsol's latest deal in recent years aimed at boosting its renewables business. The company bought renewable energy firm Asterion Energies and took a 40% stake in U.S. renewables developer Hecate Energy.
The deal is expected to close by the end of the year.