However, what I want to know is how much electrical power does that dish draw?
No system is 100% efficient, so it has to draw more than 23 watts. Maybe it's 24, 25, 50, 100, or 23.001. I don't know what the typical efficiency of a dish is when measured by electric power in versus signal power out.
Also, if I'm not mistaken, this will be the same for Voyager 1 and 2.