An estimated 63,000 properties in north Lancashire were hit by a power cut, Electricity North West has said.
The company said Lancaster's Caton Road substation went offline at 11:00 BST, leaving parts of the city and nearby Morecambe and Carnforth without power.
Power supplies resumed at 16:30 BST in the remaining 10,000 properties after 53,000 had theirs restored earlier.
The firm said it was not yet known what caused the outage and thanked customers for their "support".
A flood at the facility during Storm Desmond in 2015 left 55,000 without power.
The outage resulted in travel problems, with many traffic lights not working, and caused disruption to schools, universities and businesses.
Lancaster town hall closed while the outage was dealt with. It later reopened but Lancaster City Council tweeted it "can only deal with basic enquiries".
Salt Ayre Leisure Centre in Lancaster was closed and it only accepted cash payments when it reopened.
Lancaster University was affected and tweeted wi-fi is available outside the chaplaincy centre, security lodge and information systems services.
The university's student union sent a tweet telling students who were facing exams to turn up as usual.
St John's Hospice and Lancaster Cathedral both tweeted that power had returned.