Actually we have had a very similar visualizing before we started to count timestamps on the node in the tally reports, before it was look like this:
and when you hovered a mouse above the line, the data points were appeared, so it was like a barchart but with connected tops and smoothing.
Then after multiple complains we implemented to show not GB*h, but TB*m and the average instead of a real day usage estimated for the month, and started to match timestamps to make the graph smooth and show decreasing or increasing a usage accordingly the month average.