What size solar system should I get?

Installing solar is relatively cheap, when you consider that it pays itself off in 3 to 5 years. It will be cheaper overall to install the maximum now, than to try to upsize it in a few years, especially since you will probably only have one chance to get subsidy help. If you have the money or can use one of the government payment schemes, I suggest getting the maximum allowed 10kW system, with slightly more panels (see below).

You also need to have enough unshaded roof space to install them.

In the southern hemisphere, we aim solar panels to the north for maximum sunlight. A north facing room will produce a high peak of solar power in the middle of the day, when your demand is probably low. So, it’s typically best to place panels on east and west (or north east and north west) facing roofs to skew power to the beginning and end of the day, respectively.

On our house, we have all of our panels on a north west facing roof. This skews our production slightly to the end of the day, but the peak is still prominently around noon.

We actually have about 12kW of solar panels, funnelled through a 10kW inverter. This is known as “oversizing”. I think 30% oversizing is typical practice. It might seem like a waste, to only use 10kW of the 12kW produced. That peak is only in the middle of the day, around noon, on a high sun summer’s day. The oversizing also raises the production by 20 - 30% for the rest of the day and year, when it isn’t limited to 10kW.

What panels and installer should you use? I don’t have expertise here, sorry. I can just tell you our experience. A good source for diving into options is:
https://solarquotes.com.au

On there, you can also fill out a request for a quote. We did, which generated quotes from three providers, who suggested slightly different systems. I asked a few questions back and forth and I asked for premium options. We ended up going with Lightning Energy

The “premium options” I asked for incurred a higher cost. For example, I opted for panels that had some high tech way of managing partial shade on panels, since our neighbour’s tree was going to move some shade across our roof at the end of winter days. In hindsight, I’m not sure that these options made much difference, since some level of shade handling is standard. As I mentioned, I’m not an expert on panel options.

You can see the nitty gritty details of our installation in this post from two years ago:
https://www.facebook.com/share/1Gd8p5a594/

Please ask any questions here about our solar installation.

Coming up:
What do all the numbers and "kW' and "kWh" mean?: https://www.facebook.com/share/p/17oxBLb3Wy/

How do I pick a battery?
What electricity plan should I use?
What are the gotchas we wish we knew before we purchased?