When anchored in a bay we use a petrol lamp clipped to the back stay. This usually lasts from sun down to the next morning. Now I find these cute lights for gardens with a solar panel on top and super bright LEDs inside. They charge during the day and come on automatically at dawn. Something like that fixed at the back stay (or other place) could be a good anchor light needing no attention what so ever. Anyone thought into that too?
I am moored on the edge of high traffic channel, so I got one of the solar powered walkway lamps and I added a conical reflector to it, but it just is not bright enough so now I have it as well as one from Davis and is is real nice and visible for 2 miles yet it just uses a trickle of power.
Depending on the length of your boat, if you are over 4 meters, neither oild lamps or the garden lamps you describe are legal under COLREGs. In other words if you get hit in the night it is legally your fault. Get a light that meets the standards.