The 1,247-megawatt unit had not connected to the grid by 1215 PDT Friday, APS said, but was expected to be connected later Friday afternoon or by the evening.

APS is the operator and primary owner of Palo Verde, the biggest nuclear plant in the United States, with a total output of about 3,800 megawatts.

Unit 3 went offline for refueling on March 31.

The unit is one of three at the biggest nuclear power plant in the United States. The beleaguered 1,243-megawatt unit 1 at the Palo Verde power station is still offline and is not expected to return until June 30 or so, said APS.

The 1,314-megawatt unit 2 at the plant was operating fully on Friday.

One MW powers about 800 homes, according to year-round North American averages.

APS is a subsidiary of Pinnacle West Capital Corp. (PNW.N: Quote, Profile, Research)

The owners of Palo Verde are are APS (29.1 percent), the Salt River Project in Arizona (17.5 percent), Edison International's (EIX.N: Quote, Profile, Research) Southern California Edison Co. subsidiary (15.8 percent), El Paso Electric Co. (EE.N: Quote, Profile, Research) (15.8 percent), PNM Resources Inc.'s (PNM.N: Quote, Profile, Research) Public Service Co. of New Mexico subsidiary (10.2 percent), Southern California Public Power Authority (5.9 percent) and the Los Angeles Department of Water & Power (5.7 percent).