Berkshire Hathaway Energy, a unit of Warren Buffett's Berkshire Hathaway, said it would acquire Oncor Electric Delivery Company.
The deal puts Oncor's equity value at about $11.25 billion.
Berkshire Hathaway Energy said it agreed to buy reorganised Energy Future Holdings Corp (EFH), Dallas-based Oncor's bankrupt parent, for $9 billion in cash.
The deal is a bold bet by Buffett that he could win approval for the acquisition from Texas regulators, after they blocked two earlier attempts to sell Oncor, one of the largest US power transmission networks, to other companies.
"By joining forces with Berkshire Hathaway Energy, we will gain access to additional operational and financial resources as we continue to position Oncor to support the evolving energy needs of our state," Oncor chief executive Bob Shapard said.
Texas regulators in May said they remained opposed to NextEra Energy's proposed $18 billion acquisition of Oncor, a deal they said was not in the public interest.
The Berkshire Hathaway deal also represents a return to a previously soured investment for Buffett, who in 2013 lost $873m on a $2 billion bond investment in EFH.
The transaction is expected to close in the fourth quarter of this year.
