UPDATE 1-Dynegy to restate 1st-qtr revenue, cost of sales

(Adds dateline, new throughout)

NEW YORK, July 25 (Reuters) - Power producer Dynegy Corp (DYN.N: Quote, Profile, Research) will restate its first-quarter results to reduce its revenue and its cost of sales by $229 million due to a calculation error, the company said on Friday.

The restatement does not effect its previously reported loss for the quarter, nor does it hurt its cash flow or forecasts for 2008, Dynegy said.

It said that because of the error, its revenue and cost of sales included $229 million of power purchases that were presented on a gross basis instead of a net basis.

It plans to file an amended quarterly report with the U.S. Securities and Exchange Commission. The company reported its first-quarter results on May 8.

Shares of Dynegy closed at $6.77 on the New York Stock Exchange on Thursday. (Reporting by Michael Erman; editing by John Wallace)