Pros
It is a large company with a variety of different roles to be fulfilled and it operates in many States around the country. The pay is probably on par with most publicly-traded energy providers. If the Fortune 500 environment is for you, then this might be a good place to work.
Cons
It is too large of a company, with little regard for employees. There is a culture of micromanagement. It has a very corporate structure, with changes that seem to be constant and always for the worse. NRG is growing the business too fast for things to be done properly, so many substandard projects are rolled out before they should be. Management seems to be focused on purchasing as much of the competition as they can, instead of trying to build a better alternative.