Tampa Bay failed on four power plays and is 0-for-13 with the man advantage in its last four games.
Giroux put the Flyers ahead with a one-timer from the circle as he fell forward at 13:01 of the first period on a power play. Simon Gagne assisted on the play for his 500th point in his 626th NHL game. Philadelphia teammate Danny Briere posted his 500th point in his 626th career game Wednesday against Toronto.
Hartnell, who broke a 17 game scoreless drought, made it 2-0 at 3:36 of the third period, scoring on a breakaway pass from Briere.
"It's probably one of the longest stretches I've had without scoring other than my first 20 games here with the Flyers," Hartnell said.
After St. Louis scored on a give-and-go with Steven Stamkos at 13:05 of the third, Betts put in a rebound at 16:55. He added an empty-net goal with 27 seconds remaining.
"That third goal was a game-changer," Stamkos said. "It broke any momentum we had. That was a tough one to swallow."
Tampa Bay's suspended game against the New Jersey Devils on Friday will be resumed Sunday night in Newark, N.J. The Lightning led 3-0 in the second period when lights went out in half the arena. ... The Lightning are 4-1-1 in the second half of back-to-back games. ... Flyers C Mike Richards, who also assisted on Giroux's goal, has 16 points in 16 games against the Lightning.
Copyright by STATS LLC and The Associated Press
Arena: Wells Fargo Center Location: Philadelphia, Pennsylvania
Referees: Tim Peel, Justin St. Pierre Linesmen: David Brisebois, Jonny Murray
Attendance: 19,678 (100.9% full)
Team Stat Comparison
Power Play Goals
Power Play Opportunities
Shots on Goal
Claude Giroux (9)
(Power Play) Assists: Mike Richards, Simon Gagne
No scoring this period
Scott Hartnell (10)
Assists: Daniel Briere, Chris Pronger
Martin St. Louis (11)
Assists: Steven Stamkos, Steve Downie
Blair Betts (5)
Assists: Ian Laperriere, Braydon Coburn