In Perth, WA the ideal position for solar hot water system panels or solar power panels is facing true north on a 30 degree pitch.

Most homes have a 18 – 22 degree roof pitch, so this can result in a 2 – 3%  drop in efficiency, if facing due north.

If you can’t have the panels north facing then they can be placed facing east or west. Facing due East or due West on a 20 degreee roof pitch will reduce solar efficiency 13%.

Solar panels must never be placed with any southerly aspect as they will not get enough sun to work efficiently.

You can purchase a mounting system, for use on flat roofs, which has a pitch of 30 degrees.

East Rather Than West Facing

With solar hot water systems panels facing east or west, you may need to add an extra panel to generate sufficient hot water.

With solar power panels facing East or West you will not generate as much electricity as if they are facing due North.

I prefer solar panels to face East rather than West, although potentially they generate a little less solar hot water or solar power because you are getting the early morning sun. Solar panels need sunlight not heat.

For a hot water system this means from dawn the sun will be heating your hot water when there is potentially a whole family wanting showers. Also, if your solar hot water system dumps overly hot water,  you don’t want it to get the hot westerly sun as you will end up wasting water.

Solar power doesn’t work as well in high temperatures and the panels are a lot hotter than the ambient temperature so the tiny drop in power from an Easterly facing panel over a Westerly facing panel will be less than the drop in power output because the higher temperatures encountered by West facing panels.