The largest stockholder in a corporation providing electricity-delivery data services to the retail energy industry was subject to an unfair merger and is entitled to $15.9 million more than he was paid when his stock was cashed out in the merger, Delaware Court of Chancery Chancellor Andre G. Bouchard has ruled.

Nathan Owen, who held 35.2 percent of the company’s shares, received $26.3 million, or $19.95 per share, when he was cashed out of Energy Services Group Inc. in May 2013. ESG merged with Acquisition Corp. into a company still known as Energy Services Group.