All of us down under know that solar panels should be placed on the North facing roof.

Exactly how much is the difference in power production between a system with all panels facing North and a system where the solar arrays are split between East and facing roof?

Here is our attempt to put a percentage figure to this question. The figures below are results from modelling the difference for a 5kW system using SMA design software for a location in Perth with panels pitched on  a 20 degree roof.

Months Solar Generation
North Facing Array (kWh) East-West Split Array (kWh) Percentage Difference
Jan 30.7 30.9 -1%
Feb 28.3 27.5 3%
Mar 26.9 23.7 13%
Apr 20.4 16.6 23%
May 17.3 13.0 33%
Jun 15.2 11.1 37%
Jul 15.1 11.3 33%
Aug 19.9 15.8 25%
Sep 24.1 20.8 16%
Oct 27.2 25.6 6%
Nov 30.5 30.3 1%
Dec 31.5 32.0 -2%


We can see from the above figures that the panels facing North could produce as much as 37% more power than those facing in the East/West direction in the winter months. However, the difference is negligible in summer.

In summer, the Sun is right above the Southern Hemisphere. So looks like it doesn’t really matter where you orient your panels. In winter though, the sun is much further away in the Northern Hemisphere, which makes the panel orientation more important.

However, don’t panic if you don’t have a perfect North facing roof. One possible advantage of splitting the panels between the east and west roof is that your solar generation is more evenly spread across the day. Depending on your load profile, this might work out more beneficial in terms of actual usage.