Blackouts were reported across the Midlands, the South East, South West and North East of England, and Wales.
Some 300,000 people were hit across London and southeastern part of the country, while 500,000 were hit across Western Power Distribution's network.
Hundreds of people were stranded at King's Cross station as trains were delayed and cancelled.
By 9 p.m., more than 1,000 passengers appeared to be stranded at King's Cross, with London North Eastern Railway and National Rail advising customers against all travel.
Traffic lights in some areas also stopped working.
The Department for Transport had said "Today's (Friday) power outage has had knock on impacts on travel.
"We're working hard with Network Rail and others to ensure systems are up and running as quickly as possible, so that everyone can complete their journeys safely."
Passengers at Newcastle Airport said the power cut out for about 15 minutes, but Heathrow, Gatwick and Luton airports said they had not been affected.