The contract is the fifth time that capacity at the plant has been expanded.

NCC was the lowest bidder for the engineering, procurement, construction and turbine supply contract after submitting an offer of SR3bn ($802m) earlier in 2007.

The Middle East Engineering & Development Company, a joint venture between a local business and a South Korean company, and Al-Fanar Construction Company also from Saudi Arabia, won associated packages on the project, bringing the total value of the three contracts to SR3.8bn.

Saudi Electricity Company is the client.