Aguero opened the scoring in the first half before adding two goals after the break to complete his 13th career hat-trick and ninth in the Premier League. Only Alan Shearer, with 11, has scored more in the competition.
“I never saw him like this since I was here,” Guardiola said.
“He is in an incredible condition with the ball and without the ball.”
The defending champions, who beat Arsenal 2-0 in their opening match, lost only once at home in 2017-18, and victory never looked in doubt against a Huddersfield team who have now been beaten in their first two games.
The Terriers did manage to hold City at bay for 25 minutes but were undone when goalkeeper Ederson picked out Aguero with a pinpoint pass and the striker drew out Ben Hamer before lifting the ball into the net.
Gabriel Jesus added a second seven minutes later with a crisp low strike from the edge of the area, before Aguero pounced on a Hamer error to stab in his second.
Jon Gorenc Stankovic gave the visitors the slightest glimmer of hope before half-time when he poked in from Steve Mounie’s flick-on, but any optimism was snuffed out early in the second half by a brilliant free-kick from David Silva.
Aguero wrapped up his hat-trick with a smart flick from Benjamin Mendy’s cross – before a Terence Kongolo own goal sealed an emphatic win for an impressive City.
Guardiola’s side are top of the table and have scored eight goals in two games, conceding just one. Huddersfield, meanwhile, drop to the bottom on goal difference.
“We started better than last season,” said Guardiola. “We made a good performance in 90 minutes.
“Last season, Huddersfield played five at the back. We decided today we would play with two strikers.”
How do you stop a team like Manchester City? That was a question posed to the 19 other Premier League clubs last season, with many opting for the tactic of ‘parking the bus’.
City usually managed to find a way through, but sometimes not until very late on – winning goals against Huddersfield, Southampton, Bournemouth and West Ham last term did not come until after the 80th minute.
That has perhaps prompted Guardiola to find an alternative tactic to deal with defensive sides, as BBC Radio 5 live pundit Leon Osman observed during Sunday’s game.
“Pep Guardiola has made a number of changes and left out Leroy Sane, Raheem Sterling and Kyle Walker,” said the former Everton midfielder.
“He’s taken out all the guys with pace and got his footballers on. Guys with quick feet that can operate in small spaces.”
The result was Huddersfield could barely get the ball off their hosts as City skilfully crafted opportunities from the limited space they had.