US-based Duke Energy said the cost of the coal-gasification power plant it is building in south-western Indiana has risen by $150m.

The rise will boost the project’s estimated price to $2.5bn, nearly twice the original estimate, the company said.

Duke Energy said in documents filed with the Indiana Utility Regulatory Commission that the 630MW plant’s cost has gone up because its design has required more steel, piping, electric cable and other materials than originally expected.

The plant is being built along White River near Edwardsport, about 15 miles north-east of Vincennes, replacing a 160MW coal-fired plant that Duke currently operates at the site.