By midday, however, trains were back in operation, but with major delays.
The outage halted much of the rail traffic near Stockholm's central station, affecting long-distance and commuter lines as well as the Stockholm metro.
"There's a problem with the electricity and we're working to find the source. We don't have any forecast for when it will be fixed," Roger Falk from the Swedish Transport Administration (Trafikverket) told the TT news agency.
In the wake of the outage, there was no rail traffic heading north out of the capital.
“The trains are standing still from Sundbyberg and northwards,” said Veronica Aasa, spokesperson for SL, to TT.
Long-distance trains travelling to Gothenburg via Västerås in central Sweden were also at a standstill, according to the Transport Administration.
In addition, the blue line of Stockholm's metro was left idle between Hallongbergen and Akalla.
One commuter stuck on an idle commuter train just north of Stockholm tried to take the delay in stride
"Well, what can you do about it? This is something that happens fairly often, it's completely out of our control. We can only wait,” Raymond, a native of Switzerland, told The Local.
“Back home in Switzerland we don't see this so much, but it's not the biggest problem, we'll get there eventually.”
Another commuter, stuck in Sundbyberg waiting for replacement buses to take him north of the capital was more annoyed.
"Where are the staff and why is there so little information?" he asked The Local.
"There's a bus every ten minutes or so but more people are arriving constantly."
Meanwhile, on one stalled train on the Märsta-Stockholm commuter rail line, travelers were calm, many taking solace by turning their attention to their smartphones, iPads, and personal music players.
One man even took out his electric guitar and began strumming.
The Arlanda Express train connecting Stockholm's central rail station to Arlanda airport was also left stuck on the tracks.
According to the company's website, a "comprehensive signal problem" is to blame.
Later on Friday morning it emerged that the outage stemmed from a problem with power supplier Vattenfall.
"We're got people out in the field working to address the problem," Vattenfall spokesperson Magnus Kryssare told TT.
"It's a combination of problems, partly with us, partly with the Transport Administration."
By midday, Vattenfall had fixed the problem, allowing trains to once again roll out of Stockholm's central station, but lengthy delays continued.