Mirant Pittsburg, California, Unit 7 off-line

LOS ANGELES, May 13 (Reuters) - The 682-megawatt Mirant Corp (MIR.N: Quote, Profile, Research) Pittsburg, California Unit 7 power plant was off-line as of Tuesday afternoon, in part because of unplanned maintenance, the California Independent System Operator said in a Tuesday report.

The natural gas-fueled power plant in Contra Costa County near San Francisco is owned by Mirant, which has a tolling agreement to sell power the unit makes to Pacific Gas & Electric Co, a unit of PG&E Corp (PCG.N: Quote, Profile, Research).

The unit was listed on Monday as curtailed by 162 megawatts, which were out for planned work. On Tuesday, the plant was listed as fully off-line (all 682 megawatts) for both unplanned and planned maintenance.

There are two other units at the station -- the 312-MW Unit 5, the 317-MW Unit 6 and Unit 7.

A megawatt in California on average can supply between 650 and 700 average homes with electricity. (Reporting by Bernard Woodall; Editing by Christian Wiessner)