** Gas generator maker ERock's EROC.N shares fall 9.3% in NYSE debut

** Stock opens at $20.10 apiece vs $21.50 IPO price, valuing the firm at $5.49 billion on a fully diluted basis

** Houston, Texas-based EROC sold 27.9 million shares at midpoint of marketed range of $20 ​and $23 apiece to raise $600 million

** Debut comes as volatility has picked up in recent days amid renewed geopolitical tensions and rate hike concerns

** ERock, founded in 2006, ​provides natural gas generators to data centers, utilities, and commercial and industrial customers

** EROC has grown rapidly in recent months on the back of booming demand for alternative power systems from data centers

** "Despite this growth, ERock remains a 15-year-old company that has yet to achieve operating profitability. To support a premium valuation, management will need to demonstrate that it can convert its sizable backlog into sustainable, profitable revenue" - Troy Hooper, co-head of equity capital markets, Americas, at Mergermarket

** Morgan Stanley and J.P. Morgan were joint lead bookrunning managers for offering