Investors looking for stocks in the Utility - Electric Power sector might want to consider either AES (AES) or Unitil (UTL). But which of these two stocks presents investors with the better value opportunity right now? Let's take a closer look.Everyone has their own methods for finding great value opportunities, but our model includes pairing an impressive grade in the Value category of our Style Scores system with a strong Zacks Rank. The proven Zacks Rank puts an emphasis on earnings estimates and estimate revisions, while our Style Scores work to identify stocks with specific traits.Currently, AES has a Zacks Rank of #2 (Buy), while Unitil has a Zacks Rank of #4 (Sell). This system places an emphasis on companies that have seen positive earnings estimate revisions, so investors should feel comfortable knowing that AES is likely seeing its earnings outlook improve to a greater extent. But this is only part of the picture for value investors.Value investors also tend to look at a number of traditional, tried-and-true figures to help them find stocks that they believe are undervalued at their current share price levels.Our Value category grades stocks based on a number of key metrics, including the tried-and-true P/E ratio, the P/S ratio, earnings yield, and cash flow per share, as well as a variety of other fundamentals that value investors frequently use.AES currently has a forward P/E ratio of 14.15, while UTL has a forward P/E of 26.77. We also note that AES has a PEG ratio of 1.67. This metric is used similarly to the famous P/E ratio, but the PEG ratio also takes into account the stock's expected earnings growth rate. UTL currently has a PEG ratio of 6.14.Another notable valuation metric for AES is its P/B ratio of 2.33. The P/B ratio is used to compare a stock's market value with its book value, which is defined as total assets minus total liabilities. For comparison, UTL has a P/B of 2.51.Based on these metrics and many more, AES holds a Value grade of A, while UTL has a Value grade of D.AES stands above UTL thanks to its solid earnings outlook, and based on these valuation figures, we also feel that AES is the superior value option right now.Want the latest recommendations from Zacks Investment Research? Today, you can download 7 Best Stocks for the Next 30 Days. Click to get this free report The AES Corporation (AES): Free Stock Analysis Report Unitil Corporation (UTL): Free Stock Analysis Report To read this article on Zacks.com click here.