The two nations come face to face again this Sunday, in the first of five 50-over fixtures in the Gillette series.
But because many members of England's ODI squad were not involved in the losing Ashes series, including Plunkett himself, the 32-year-old Yorkshire fast bowler believes the team will be "full of beans" when hostilities resume in Melbourne this weekend.
Plunkett last wore an England jersey in September, when he played against the West Indies at Southampton, and looking ahead to the opening 50-over game, said: "Australia are a good team and they're confident from the Ashes.
"But it is a different squad and a different unit here. A lot of our guys didn't play in the Ashes, so we're full of energy and full of beans.
"Some of the guys have been out here playing in the Big Bash, lads have been all over the world playing, so we're full of confidence and looking forward to that first game.
"It's a massive challenge against one of the best teams in the world. We're looking forward to doing battle with them and trying to take this series.
"It's always a test when you come to somebody else's backyard. To get a win out here is pretty big."
Gillette Series dates
1st ODI - Sunday, January 14: Melbourne
2nd ODI - Friday, January 19: Brisbane
3rd ODI - Sunday, January 21: Sydney
4th ODI - Friday, January 26: Adelaide
5th ODI - Sunday, January 28: Perth