This solarbooks.com.au article explains solar modules for cabins and RVs. Space is often the major limitation so buy the most efficient modules.

Solar Modules for Cabins and RVs, Solar Modules for Cabins and RVs

With solar modules for small cabins and the smaller RVs, by far the greatest use is powering a compressor fridge below 220 litres. Never use two small (say 110 litre) fridges, rather than one larger. Their combined draw will be about that of a single one of 350 litres.

Again, for the smaller cabins and RVs, it is best to confine solar to lighting, water pumping, TV, laptop computer etc. Use LP gas (or diesel) for heating and cooking. If not done already use LEDs lighting only. Avoid the eBay cheapies – the more costly LEDs produce far more light per watt.

Solar Modules for cabins and RVs – what to buy?

Solar modules vary (from 12% to 20%) in their ability to turn sunlight into usable electrical power. Where space is at a premium, buy the most efficient solar modules on the market. They are likely to be monocrystalline but the very best polycrystalline solar modules are now equally efficient. Here too, it pays to buy the best: currently (mid-2019) they cost about A$2 per watt. 

Flexible solar modules are convenient for RV with curved roofs – but typically produce only two/thirds of the output of the better quality rigid modules. Most rigid solar modules weigh about 10 kg per 100 watts, but there are rigid solar modules that weigh only 3 kg per 100 watts. Currently, however, most are very expensive.

Solar Modules for cabins and RVs – how much capacity?

Solar capacity in 2019 is less than 10% of its 2010 cost. Battery capacity, however, is only about 50% more. Always have the most solar that you can. This will not only ensure batteries charge much faster. It will enable charging even under light cloud. There is a zero risk of overcharging. The solar regulator will limit otherwise excess charge.  

Further Reading

Full details of all aspects of this and all you need to know is in our books Solar That Really Works!, Solar Success and Caravan & Motorhome Electrics. They are now obtainable in digital form directly from this website (click on the book title above). They are also available in print form from all branches of Jaycar in Australia and New Zealand, they can be ordered from any bookshop in Australia or via email from booktopia.com.au.