Good point. Making the RPi talk RS232 to the ancient WattsUp took only a level shift and decidedly retro baud rate (the summary said "outdated"). (FYI, there's now a "net connected" WattsUp, but they want you to go through their proprietary portal: NFW! Hunk of junk!)
I probably should've mentioned that I initially used Google Analytics to build the graphs. It's really not designed for that.
The duct tape-like approach I took with hardware I had sitting around to bend it to my will (vs. buying something off the shelf - not to mention final fit and finish) make it feel like a hack to me.
But OK, point made. I DQ myself.