Updated July 2017
Ideally, solar panels face directly into the sun and was often done using costly tracking systems. It is now, however, simpler and cheaper to add more solar capacity to compensate.
Author’s current 2.4kW system overlooks Pittwater (Sydney, Australia). Pic: successfulsolarbooks.com
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. If exact orientation is not feasible, have them face a little West. Not East.
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 50–100 lower. Likewise, for more input in summer have them 50-100 higher. Some people have adjustable racks. Here again, however 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. +/- 350 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 thus 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.