The two companies' service divisions will be joined to offer O&M across North America, Duke said.
"The agreement offers a one-stop shop for customers who are managing multiple brands of wind turbines in their fleet, helping them stay competitive and derive maximum value from their wind energy assets," said Duke Energy.
It "means the market now has a new and powerful choice", the developer added.
The move adds competition to Vestas' multi-brand servicing offering formed when the Danish manufacturer acquired UpWind Solutions in December 2015.
According to Make Consulting, the $2-billion North American service market will grow to $2.75 billion in annual spending by 2021.
That includes in-house servicing, which more of the US's typically large owners are moving towards in order to leverage economies of scale. The global market will grow from $9.7 billion in 2015 to $19.3 billion in 2024.