The Premier League champions remain unbeaten after their 3-1 win at home to Queens Park Rangers added to their victory over Southampton and draw at Liverpool.
However, Hart has admitted that despite their good start, City are far from their best form.
"It's a good start but I think we could have done better in all three games, if I'm being totally honest. It was a tough draw away at Liverpool and we made our two home games [against Southampton and QPR] hard work but we've got the points on the board," Hart told talkSPORT.
"I don't think we've really been up to standard if we're being brutally honest about the way we're going to be. We pride ourselves on not conceding goals and definitely not giving goals away like we have done but that's the way it is in the Premier League.
"Luckily we've got the firepower. We never really feel it's the end of the world if we do concede a goal and that's definitely not an attitude to rely on but at the moment that seems to be helping. Hopefully the Premier League will settle down now that it's September and hopefully we'll go back to usual."
City currently find themselves fourth in the Premier League table.