US private equity firm KKR is to buy a one-third stake in the energy arm of Spain's Acciona for €417m, the companies said on Tuesday, as they move to develop one of the world's largest renewable energy portfolios.
It was the latest asset sale by a Spanish renewables energy firm after regulatory changes in Spain to cut costly subsidies.
The government measures have particularly hurt profit at Acciona's wind farms.
The deal gives Acciona Energia International (AEI), the international renewable energy generation arm of Acciona Energia, an enterprise value (equity plus debt) of €2.6bn, in one of the world's biggest-ever deals in the renewable energy sector.
Half of that enterprise value is in equity and half in net debt, the companies said.
The portfolio will include Acciona Energia's operating renewable assets outside Spain, amounting to 2.3 gigawatts across 14 countries including the United States, Italy and South Africa.
The assets largely consist of wind farms, with a few solar plants.
The companies are also planning an initial public offering through a vehicle that will hold all or part of AEI's assets.
The public offering would be for a so-called yieldco vehicle, similar to a spin-off by another Spanish renewable energy firm Abengoa (ABG.MC), which recently made public its US subsidiary Abengoa Yield (ABY.O).
Yieldcos usually own and operate some assets of their parent companies and have long-term purchase agreements with power utilities, a guarantee of stable cash flow.
The KKR-Acciona deal is expected to be closed before the end of the year.
Shares in Acciona were last trading up 3.5pc at €67.24.