On Apr 5, Zacks Investment Research upgraded Black Hills Corporation BKH to a Zacks Rank #1 (Strong Buy).Why the Upgrade?Black Hills Corporation has been witnessing a rise in earnings estimates on the back of strong fourth-quarter 2015 results. This diversified energy company has been a consistent performer, reporting positive earnings surprise in three out of last four quarters, with an average surprise beat of 18.54%. The long-term earnings growth of the company is pegged at 4.61%.Incidentally, 2015 marked the sixth consecutive year of earnings growth for Black Hills Corporation, thanks to its strong operational performance. This can be credited to the excellent electric utility performance and solid performance in its power generation and coal mining segments.The ongoing capital projects will help it provide quality service to its customers. In addition, the completion of acquisition of natural gas utility SourceGas Holdings LLC, on Feb 12, 2016, will add nearly 429,000 customers in Arkansas, Colorado, Nebraska and Wyoming, and a 512 mile regulated intrastate natural gas transmission pipeline in Colorado to Black Hills Corporation existing assets.Recently, Black Hills Corporation announced an increase in its annual dividend for the 46th consecutive year. No doubt it is a testament of its effort to build long-term value for its shareholders.The Zacks Consensus Estimate for 2016 moved up 7.9% to $3.00 per share as 50% of the estimates were revised higher over the last 60 days. For 2017, 50% estimates were revised higher over the same time frame, raising the Zacks Consensus Estimate by 1.2% to $3.42 per share.Other Stocks to ConsiderApart from Black Hills Corporation, Atlantic Power Corporation AT also sports a Zacks Rank #1 (Strong Buy). Other top-ranked stocks in the utility power space include CMS Energy CMS and Calpine Corp. CPN. Both hold a Zacks Rank #2 (Buy).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 >>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 CMS ENERGY (CMS): Free Stock Analysis Report CALPINE CORP (CPN): Free Stock Analysis Report BLACK HILLS COR (BKH): Free Stock Analysis Report ATLANTIC PWR CP (AT): Free Stock Analysis Report To read this article on Zacks.com click here. Zacks Investment Research