Again this is such a tricky one to answer as your needs will vary. You need to do an energy audit (listing all the appliances you are going to use, how many amps they draw per hour and then how many hours you are going to use them in a day) once you have all of that information you can see how big a set up you’ll need. Here’s a solar kit we bought for our first van, it had everything we needed except the battery (https://ukvanlife.co/solar-kit). For more info on batteries check out this groups article on them here: https://ukvanlife.co/campervan-battery/ As a rule of thumb, you're going to need two leisure batteries and at least 200W of solar to try and run a fridge in the UK year round and the same if you want to run a diesel heater in the winter in the UK.