At the time your utility approves your interconnection, an installation normally lasts 1 to a few times for residential rooftop; for a longer time for floor mount. The best way to determine the number of panels you may need should be to evaluate your electricity usage at distinctive instances on https://medium.com/@solarsystemaustralia/choosing-the-best-solar-installers-in-wa-for-maximum-energy-savings-a318bd7035a5