The firebrand England international has consistently scored around 20 goals per season, with his most prolific campaign coming in 2006/07, when he reached 23 in all competitions. With 11 already this term, he is hopful of surpassing that.
"Of course, taking penalties, my tally should be a lot higher," Rooney told MUTV. "Thankfully I've scored two of them today. It's a great feeling to score a hat-trick, an amazing feeling."
Rooney's first penalty at Fratton Park came in a hotly-contested first 45 minutes in which Portsmouth enjoyed the better openings, and the striker conceded that United were made to work for the points.
"It was quite difficult in the first half. The manager was disappointed we didn't move the ball round as well as we can, and we didn't create that many clear cut chances," he said.
"We had to try and work on that in the second half, and we got the goals and could ease off. But overall it was a difficult game and we're really pleased with the three points."