NextEra Energy is in advanced talks to buy rival utility Dominion Energy in a deal that would be one of the largest of the year, according to people familiar with the matter. Florida-based NextEra has a market value of nearly $200 billion, while Virginia-based Dominion has a market value of around $50 billion. NextEra owns Florida Power & Light, the largest electric utility in the U.S., and is also a large developer of power generation and transmission.