We've just had a 5.4kW solar system installed which involved a lot of prior research, so I thought I'd share for those interested.
Stiffy, speak to Glen Clark before you sign with anyone.
http://www.glenclarkco.com.au/. He makes a free site visit to measure light levels, roof orientation, shade from trees and chimneys, etc and provides a detailed report - no obligation. By far the most thorough of the half dozen installers I spoke to and great to deal with. Price was right too.
We're using two "strings" of panels oriented NNE and NW thanks to our roof line. On a clear summer morning the NNE array starts making power at 6.10am and the NW facing array is still generating a bit of power at 8.30pm. We're producing 35-40kWh per day in summer and sitting around 5kW/h in the middle of the day, which is excellent for a 5.4kW system when you allow for losses.
There is no magic number of panels to have in each string, as panel outputs vary wildly - as do site requirements. Newer panels generally produce more power for their size (more efficient), plus panel quality even in tier 1 panels can vary greatly. I was told by one installer that the cheaper systems all use panels that are rejected from the B-grade batches, they're that bad.
If shade is a problem you can opt for micro inverters (per panel) which allow the panels that are not in the shade to generate power. With a normal (single) inverter the shaded panels dramatically reduce the ability of the whole system to make power. With cheap systems a few stray leaves or large bird droppings can lower the voltage enough to knock out a whole array. Stay right away from those $3000 systems on TV!
I went for the LG Mono X Black panels to blend in with the roof and a German built SMA inverter which you can just see inside the garage behind my lovely wife. The inverter logs data and has bluetooth so you can upload and monitor remotely, if you're a bit of a nerd like me.
And a couple of photos.
