Exhibit 15 1345 Avenue of the Americas New York, NY 10105 May 14, 1998 KeySpan Energy Corporation One MetroTech Center Brooklyn, NY 11201 Gentlemen: We are aware that KeySpan Energy Corporation has incorporated by reference in its Registration Statement Nos. 33-66182, 333-04863, 333-03441, 333-06257 and 333-18025, its Form 10-Q for the quarter ended March 31, 1998, which includes our report dated April 30, 1998 covering the unaudited interim financial information contained therein. Pursuant to Regulation C of the Securities Act of 1933, our report is not considered a part of the registration statements prepared or certified by our firm or a report prepared or certified by our firm within the meaning of Sections 7 and 11 of the Act. Very truly yours, ARTHUR ANDERSEN LLP