Van Persie has netted nine goals in 12 matches for his new club and Giggs thinks the striker's performances have given everyone a lift after United lost the English Premier League title to neighbours Manchester City last season.
"When a ready-made, world-class player comes in it gives everybody a lift," Giggs told reporters.
"And Robin is certainly that. He's proven that with his goals and all-round play since he's come to the club.
"Robin's set-piece delivery is really important to us, it's a big plus that we're scoring from set-pieces and corners.
"That's something we haven't done over the last few years as often as we'd have liked.
"So with Robin it's not just goals you get. He's helped a few different names get on the score sheet."
Van Persie comes up against former club Arsenal on Saturday, but Giggs is not expecting a repeat of the 8-2 scoreline which occurred in the corresponding fixture at Old Trafford last season.
"Last season was one of those fluke performances," he said.
"We always expect a tough performance against Arsenal. It's no different this time."