After the market close on Monday, the cloud software provider projected 2016 full-year revenue to range between $157 million to $165 million, while Wall Street was projecting revenue of $172.14 million.
Pacific Crest Securities downgraded Opower to "sector weight" from "overweight" on Tuesday.
The slow pace of the utility industry, which Opower provides software to, is hurting the company's growth, the firm said.
"This is the second time Opower has issued lower-than-expected yearly guidance," the firm added. "Though our discussions with private companies in the utility space suggest limited competition for Opower's products, the slow-moving pace of utilities and Opower's decelerating growth lead us to downgrade shares."