It was enough to clinch victory and end any lingering relegations worries with one match left to play.
"The game certainly wasn't a classic but if anyone was going to get the winning goal there was no one more fitting than Rob Hulse," said Rams boss Nigel Clough.
"He's been excellent all season and it was lovely for him to score the winner.
"It means we are finally there and it's a huge relief. As it turned out, with the way other results went, a point would have been enough but it's nicer to finish with three points and a clean sheet at home.
"We can now start looking in earnest at next season and the biggest thing is to get the injured players back for that."
Clough knows Derby will have to improve to have any chance of mounting a challenge next season on the evidence of today's performance.
"I don't know what it was in the first half, whether it was nerves or tension but we were very lacklustre and didn't seem to have a lot of energy," he said.
"It was one of those games where everyone was waiting for someone else to do something but we got closer to them in the second half.
"At half-time we said to the players, 'Let's have a go at them'. That's what we have done in the last three and a half months and when we did that we looked a different side."
Charlton were already relegated but manager Phil Parkinson can still see reasons for optimism.
He said: "It's been tough and the summer can't come soon enough.
"We have to start rebuilding. We want to keep the good players and add to the squad.
"We need to bring in some firepower but Charlton is a big club and players should want to come and play for us.
"There's a great chance that this time next year we will be celebrating promotion.
"We were the better team in the first half but then we got sloppy and we gave the ball away too cheaply and Derby raised their game."