Perhaps frustrated by beginning his sophomore year with five scoreless periods, Ovechkin - the Calder Trophy winner as top rookie in 2005-06 - went into a prolonged celebration after putting the puck in the net 8:04 into the third period to put Washington ahead 3-2.
He kissed his right glove, pumped it, then let out a yell. He was surrounded by teammates for hugs and back-slaps, then skated over to the bench, where he shouted again as he looked up and saw himself on the overhead video board.
Five minutes later, Ovechkin scored again, this time redirecting defenceman Brian Pothier's shot from the slot on a power play to make it 4-2.
Semin, who scored in each period, added the finishing touch with 2:47 left in the game on a close-range goal. Pothier collected one of his three assists on that one, which gave Semin his first three-goal game in 54 NHL contests.
It capped quite a home opener for the Capitals, who finished 27th out of 30 NHL teams last season.
Andrew Ladd and Niclas Wallin scored for Carolina, which has yet to win in its defence of its first league title. The Hurricanes were playing their third game in four nights after consecutive losses at home, as they raised their championship banner and showed off the Stanley Cup.
Shortly after Ovechkin's second goal, he went down after Carolina defenceman Tim Gleason used his left skate to cut the Russian's left leg out from under him. Ovechkin, who had just hit Eric Staal, dropped to the ice and stayed down for a few minutes.
But he eventually returned and was the first to greet Semin with a hug after the hat trick was completed.
Semin was picked in the first round of the 2002 NHL draft and scored 10 goals in 52 games with the Capitals in the 2003-04 season. But when Washington wanted him to report to a minor league club during the NHL lockout, he instead went to play in Russia, and the Capitals sued to get him to return.
Finally, in April, he agreed to rejoin the Capitals - and they couldn't be happier.
Semin, at 22 a year older than the better-known Ovechkin, already has four goals through two games.
Notes: Hurricanes D Bret Hedican, who had off-season hip surgery, was scratched with what the team called a lower-body injury. ... Before the game, the Capitals recalled LW Tomas Fleischmann from Hershey of the AHL. ... It was the 400th game Rod Brind'Amour has played for the Hurricanes. ... Saturday's game opened a seven-game road trip for Carolina. ... Ovechkin had 52 goals and 106 assists as a rookie.