The south Londoners went ahead with a fantastic strike from Danny Haynes in the 19th minute before Jamie Ward equalised for the Rams from the penalty spot midway through the second half.
Powell was pleased Charlton demonstrated their ability to hold on in soggy conditions at The Valley, with the Addicks reduced to 10 men when Michael Morrison picked up a second booking for fouling Richard Keogh in the area.
He said: "We needed that, especially after going down to 10 men. I'm happier than Boxing Day. There were a couple of turning points.
"With Morrison getting sent off the players showed a lot of resilience. We've a lot to build on. They were testing conditions, and we dug in to get a point and we move on."
Powell added: "It was a great strike by Danny Haynes, he's been a real livewire.
"He's got tremendous pace and scored some goals for us. It was a superb goal that lifted everyone."