NextEra Energy Transmission has signed an agreement to acquire US-based independent power transmission company GridLiance.

The deal with Blackstone affiliates holds an estimated value of approximately $660m, including the assumption of debt.

Established in 2014 by Blackstone Energy Partners, GridLiance currently owns and operates more than 700 miles of transmission lines and related substation infrastructure across six states in the US.

It has also established a presence in the California Independent System Operator, Southwest Power Pool, and Midcontinent Independent System Operator regions.

GridLiance president and CEO Calvin Crowder said: “We are very excited to be joining NextEra Energy Transmission at a pivotal time in the company’s development.

“Our unique capabilities, proven track record, and tremendous growth prospects, coupled with NextEra’s experience as a leading transmission owner, make this a great fit for both companies.

“We are also grateful for the support of Blackstone in founding GridLiance and for working closely with management over several years to build the company into a leading business focused on improving transmission system reliability and partnering with public power entities.”

NextEra Energy Transmission, a subsidiary of NextEra Energy, operates in California, New Hampshire, and Texas. It also has several projects under development across the US and Canada.

Completion of the deal is subject to customary state and regulatory approvals and is expected to close next year.