We spent 8 days boondocking on the north shore of Lake Superior last year.
There are two components to this, saving energy,I designed the trailer for this exact purpose with all LED lights very efficient Morningstar 300W inverter to power DVD/TV. We use a french press for coffee...
We do have a 185W solar panel which powers as well as the rest of it a Waeco 12V refrigerator. I would also recomend the use the TV and a set of jumper cables idea and have mine set up so I can do that if bad weather/clouds prevent the solar panel doing its job. I alos have a Victron batter monitor which tells me if we approach the 50% depth of discharge below which you do not want to go.