Dynegy Downtown Houston. Image source: Flickr

What: Shares of Dynegy (NYSE: DYN), a company that operates power generating facilities in eight states across the United States, are trading more than 15% higher late Thursday after two developments hit the newsfeeds.

So what: Dynegy opened the trading day higher after reporting its fourth-quarter and full-year results after the market closed on Wednesday. For the full-year Dynegy reported $850 million in consolidated adjusted EBITDA, which was a $503 million increase over the prior year's results and in the middle to lower end of its $825 million to $925 million guidance range. Much of the full-year increase in adjusted-EBITDA was thanks to newly acquired assets.

On the downside, management lowered its 2016 adjusted-EBITDA guidance to between $1 billion and $1.2 billion, down from $1.1 billion to $1.3 billion. It also lowered its 2016 free cash flow guidance to $200 million to $400 million, down from $300 million to $500 million.

 "While the operating environment remains challenging due to low commodity prices and unseasonably moderate weather in the fourth quarter, we achieved our financial targets benefiting from our fuel and geographic diversity and ended the year with $1.5 billion in liquidity." said Dynegy President and Chief Executive Officer, Robert C. Flexon, in a press release.

Now what: With the fourth-quarter and full-year results only briefly available, investor attention turned to the announcement of Dynegy and Energy Capital Partners forming a joint venture to acquire ENGIE's United States Fossil Portfolio. It's a move that investors liked, sending the stock price roughly 8% higher after the announcement, and management notes that the acquisition will strengthen the company with the right assets, in the right markets, with the right structure, all at the right price.

The price checked in at $3.3 billion, or $378/kW, and the company believes it can generate $90 million in annual synergies. The deal has Dynegy and Energy Capital owning 65% and 35% of the joint venture, respectively, with Dynegy responsible for day-to-day management and operations.