Shares of NRG Energy (NRG) closed 3.17% higher at $11.38 Monday amidst a broader rally among energy stocks.

Deutsche Bank thinks that the company could have significantly more upside.

"In our view, NRG is a tremendous value play, having met or exceeded expectations consistently for two years running," analyst Abe Azar wrote in a research note circulated to investors before the market opened Monday, citing its profitable retail franchise.

One of the nation's largest electricity producers, NRG also holds large solar and other renewable energy holdings through its yieldco, NRG Yield (NYLD).

The only thing holding NRG back is the debt load of subsidiary GenOn Energy (which NRG purchased for $1.7 billion in stock back in 2012), Azar argued. He has a price target on the stock that ranges between $19 and $21.

"If GenOn can be resolved amicably and quickly, we see material upside for NRG shares," he wrote.

NRG reported third quarter earnings per share of $1.27 on roughly $3.95 billion in revenue on Friday.

NRG Chart NRG data by YCharts

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