Some years back, there was a very successful Ad campaign for a particular brand of motor oil, the catch-phrase being "Oils ain't oils Sol." I would suggest, in the context of a PV System, this phrase can be easily modified to: "Installers ain't installers Sol.".
Based on our personal experience and anecdotal evidence from various sources, choosing a "Good" Installer is not so straight-forward. To save yourself time and effort, my recommendation to ovoid this issue is to start your research through "Solarquotes.com.au"; this is where I eventually ended-up.
By using this website, I finished-up accepting the quote from 'Formosa Electrics' for our PV System (formosaelectrics.com.au). Having 'now' connected to 'The Grid', my wife and I are exceedingly pleased with our installation by the company. As part of this review, I can comfortably write that our dealings with them have been smooth and trouble-free throughout.
In working through the 'usual suspects':
* communications throughout the entire process;
* feeling part of the process;
* arriving on the agreed date/time for a pre-install 'site inspection';
* arriving on the agreed date/time for install (always subject to 'weather permitting'!);
* arriving at the expected start-time;
* completion of install on expected date;
* no unexpected [dollar] 'extras';
* high-quality, professional installation;
* site clean-up after install, and
* invoicing processes.
Even though 'online reviews' are limited to a 'five' rating, against each of these I/we give them a '10 out of 10'. (I should include that being 'somewhat[!?]' of a perfectionist, 'My' standards and expectations are generally above the norm.) We even received drone-video footage of the installation!
At the nitty-gritty level, "Joseph" (Owner and Installer) handled all the paperwork-type requirements necessary to get our PV System up-and-going. You still have do the government rebate part yourself; no avoiding it! (That rebate 'experience' should give you an idea of how much time, effort and anguish you can avoid by Joseph completing key requirements on your behalf.)
Some recommended takeaways from our experience are:
(1) Take the time to do your research properly, i.e., your current and future needs.
(2) Look for a company with a 'proven' track-record, e.g., 'reputable' reviews.
(3) 'Smaller' company's tend to be more personal.
(4) Effective communications are essential between you and the installer.
Finally, I would suggest you would be hard-pressed to find a similar company as professional as 'Formosa Electrics' for your PV solar installation. "Truly excellent work guys!"

Approximate cost: $10000

Joseph from Formosa Electrics installed a solar panel system recently as well as completed some other electrical work.

After getting several quotes from other bigger businesses, Formosa was miles ahead in terms of value for money, reliability and honesty.

Best of all though, all jobs undertaken were completed so neatly and cleanly. This guy is a true perfectionist.

Will be using Formosa Electrics for all future electrical work and recommending them to family and friends.