Solar Panels - What's Your Angle?

A friend recently asked me about how well solar panels would work on her east-west roof.

The perfect direction (in the southern hemisphere) is north-facing. But some people (including my neighbour) do face panels west or east if that's the way their roof faces. So how much sunshine do these panels get?


The above diagram (for the UK) and this table (California) illustrate the difference. Here in the southern hemisphere, the same theory applies - just change south to north. So even facing dead-east, a panel still gets 85% of the sunshine that it would get facing north.

The diagram also shows the effect of "tilt angle". The ideal tilt is the same as the latitude of your town. Here in Brisbane it's about 27.5 degrees - not too different from the average roof. But as shown in the diagram, there's a lot of leeway before sunshine is affected much.

Hope that helps. Feel free to comment if anything is confusing.