Ideally, solar panels face directly into the sun at all times. This was often done in the early days of solar by using costly and complex tracking mechanisms. Solar panel prices have since fallen so much however that it is far cheaper to accept that some loss and add more solar capacity to compensate.

There’s no need to have solar panel orientation exact. In the southern hemisphere they should face true South. In the northern hemisphere they should face true North.  

For optimum year-round input they should be tilted at the same angle as the latitude of where they are located. To establish your latitude using Google, enter the name of your closest big town plus ‘latitude’. Errors of plus/minus five degrees make little yearly difference. If you want more input in winter have them 5-10 degrees lower. For more input in summer have them 5-10 degrees higher. Some people have adjustable racks but here again it is simpler to add more solar capacity.

Full details of every aspect of this (for homes and properties) is covered in my book Solar Success.

Caravan & motor home use 

Here, some compromise is necessary. In temperate areas (e.g. +/- 35 degrees latitude) mounting solar modules horizontally results in only minor loss (typically 20%). This is readily compensated by adding 20% more solar capacity. Many caravan and motor home users also carry portable solar modules that they place facing the sun.

Full details of every aspect of solar in camper trailers, caravans and motor homes is in my companion books Solar That Really Works! and Caravan & Motorhome Electrics. Clicking on the latter will automatically transfer you too our companion website (caravanandmotorhomebooks.com) – where there are a large number of major articles on all aspects of solar in RVs.