With a 100 Watt solar panel you can run all of your 12v appliances indefinitely in the summer. Solar panels also produce power in the winter unless it is very overcast. No more need for electric hook-ups - camp in the pretty spots!
Typically, during the day, the solar panel charges your leisure battery (or your starter battery if you don't have a leisure battery) and then when it's full any excess power goes straight to your appliances. At night time, when the panel is no longer producing any power, your appliances run off the battery until the panel recharges it the next morning, and the cycle continues.
The trick is to use a panel large enough to get the battery charged fast in the morning, and then provide enough power to run things like your fridge, phone chargers etc during the day, leaving the battery full and ready to go back into service at night time. I have extensively tested 80 Watt panels and they produce enough power to keep up with 12v compressor fridges with power to spare. But remember, this kit is 100 Watts !
Keeping the beers cool
In my tests my battery ended up with a greater charge at the end of each day than it started with! - This was with running a 12v Waeco fridge, plus other things like phone charging, listening to music etc. With a 100 Watt panel you can camp in the summer, running a fridge, indefinitely with power to spare!
With current technology, 100 Watts is the largest panel that fits on the Bongo roof without covering the sunroof, is not too heavy, and does not protrude from the sides.
Below is a real (I recorded this in my Bongo) data log graph of the voltage of a leisure battery with a 12v compressor fridge running full time, cold enough for ice in the freezer section. This was "only" with an 80 Watt panel.
As you can see, the battery ends the day at midnight with the same (actually a little more) charge as is started the day with at 00:01 am - and this was in April 2012! - not June or July! (the downward spikes on the graph are when the fridge switches on for a few minutes until it's thermostat switches it off again) . In summer it is not unusual for the battery to end the day with more charge than it started with, and to be up to over 13 volts by 10/11 am.