I have this same "composting"
head installed on my sailboat, installed 1.5 years ago. I have been very happy with it. The fan
power draw is negligible, in the mA range. I have connected it directly to the house bank. The main draw is when you press the button to stir the solids, but even then, it is a very small
power draw.
For those wondering about usage and dealing with waste, there is definitely a
learning curve and some period for adjusting some habits (similar to when using
marine heads for the first time). I was definitely a skeptic at first, but after dealing with holding
tanks, sanitation hoses and pumps I decided to give it a go, I'm not going back. The system is really simple and, if you are not grossed out by managing/maintaining the standard
marine heads, managing the waste generated on a system, like the Oggo, is a walk on the park, literally, the solids smell like soil and you never get in contact with it.
Cheers