We often caravan without mains. Using gas for water heating, fridge and cooker,we find that a full 85 amp battery will deliver sufficient for 4 to 5 nights use with little problem provided you are sensible. During the summer little is need for lighting, we manage 8 to 10 showers, have the radio/cd on for as long as we need and still have power to spare.
We don't bother with TV but use the opportunity to find other ways to entertain ourselves. ( You actually appreciate the TV more when you watch it less often, especially as you can be selective in what you watch having recorded it whilst away )
Caravaning teaches you to be more aware of what you use. If you fetch the water, you conserve it whilst showering...a 40 litre Aquaroll should manage 4 showers. Turn the taps off whilst lathering your hair etc. You may find the tap pressure needs re setting as the power changes from mains to battery and to be sure that the pump doesn't start running in your abscense turn it off at the panel. Likewise, make sure you have not left blown air still on, even on low, from a previous trip as this may deplete you power.Only leave the light on you need ... and don't forget to turn the awning light off when you come inside.
It's good fun being self sufficient and trying a more back to basic approach to life whilst living in a luxury caravan !Enjoy.... and resist any temptation to invest in a generator !!!!!