The outage flipped a switch for the San Francisco 49ers, but the Ravens used a last-gasp defensive stand to hold on Sunday night, 34-31.
America's biggest sporting event came to a half-hour standstill in the third quarter when most of the Superdome lights and the scoreboards went dark. By then, the Ravens had a 22-point lead.
Everything changed after that, though, and the 49ers staged a sensational rally before Ray Lewis and Co. shut it down. But there were plenty of white-knuckle moments and the Ravens (14-6) had to make four stops inside their 7 at the end.
For a Super Bowl with so many subplots, it almost had to end this way.
Flacco's arrival as a championship quarterback coincides with Lewis' retirement – with a second Super Bowl ring no less. The win capped a sensational month since the star linebacker announced he was leaving the game after 17 Hall of Fame-caliber years.
The sibling rivalry between the coaching Harbaughs went to John, older than Jim by 15 months.
"How could it be any other way? It's never pretty. It's never perfect. But it's us," John Harbaugh said. "It was us today."
At 4 hours, 14 minutes, it was the longest Super Bowl ever. Among the most thrilling, too.
The loss of power delayed the game 34 minutes and left players from both sides stretching and chatting with each other. It also cost Baltimore whatever momentum it built, and that was considerable after Jacoby Jones' 108-yard kickoff return and game MVP Flacco's three touchdown passes made it 28-6.
Back came San Francisco (13-5-1) in search of its sixth Lombardi Trophy in as many tries.
Michael Crabtree's 31-yard touchdown reception on which he broke two tackles made it 28-13. A couple minutes later, Frank Gore's 6-yard run followed a 32-yard punt return by Ted Ginn Jr., and the 49ers were within eight.
Ray Rice's fumble at his 24 led to David Akers' 34-yard field goal, but Baltimore woke up for a long drive leading to rookie Justin Tucker's 19-yard field goal.
San Francisco wasn't done challenging, though, and Colin Kaepernick's 15-yard TD run, the longest for a quarterback in a Super Bowl, made it 31-29. A 2-point conversion pass failed when the Ravens blitzed.
Tucker added a 38-yarder with 4:19 remaining, setting up the frantic finish.
Kaepernick couldn't get the Ravens into the end zone on the final three plays – there was contact on Crabtree on the final pass that appeared incidental, and Jim Harbaugh insisted it was pass interference.
Ravens punter Sam Koch took a safety for the final score with 4 seconds left. His free kick was returned by Ginn to midfield as time ran out.
In the first half, Flacco was as brilliant as Tom Brady, Joe Montana or Terry Bradshaw ever were in the NFL's biggest game. The only quarterback to win a playoff game in each of his first five seasons – his coach holds the same distinction – was nearly perfect.
It was typical of Flacco and Baltimore's postseason run. The Ravens stumbled into the playoffs with four defeats in its last five regular-season games as Lewis recovered from a torn right triceps and Flacco struggled. Harbaugh even fired his offensive coordinator in December, a stunning move with the postseason so close.
But that – and every other move Harbaugh, Flacco and the Ravens made since – were right on target. Just like Flacco's TD passes of 13 yards to Anquan Boldin, 1 to Dennis Pitta and 56 to Jones in the first half, tying a Super Bowl record.
New Orleans native Jones, one of the heroes in a double-overtime playoff win at Denver, seemed to put the game away with his record 108-yard sprint with the second-half kickoff.
Soon after, the lights went out – and when they came back on, the Ravens were almost powerless to slow the 49ers.
Until the final moments.
"The final series of Ray Lewis' career was a goal-line stand," Harbaugh said.
"It's no greater way, as a champ, to go out on your last ride with the men that I went out with, with my teammates," Lewis said. "And you looked around this stadium and Baltimore! Baltimore! We coming home, baby! We did it!"
It was a bitter loss for Jim Harbaugh, the coach who turned around the Niners in the last two years and brought them to their first Super Bowl in 18 years. His team made a similarly stunning comeback in the NFC championship at Atlanta, but couldn't finish it off against Baltimore.