This little device is an ethernet to wi-fi adapter. It connects my solar charge controller to my home wi-fi network so I can make fancy graphs. It uses 1.2 watts per hour. I know this because I measured its usage using a watt meter. I do this with everything I power from the solar batteries.
I have a hunch that this is what solar does to you, makes you compulsive about energy use. Even if (when?) I have a large grid-tied system, I imagine myself checking the daily output, and constantly thinking about how to reduce my usage to match.
On very cloudy days, this little thing has used over 45% of the energy produced by the panels. I unplugged it. For now, graphs only on special occasions.