Compare quotes on more than the total price: check the panel and inverter brands, system size, estimated annual output, included installation work and whether the price includes GST and applicable incentives such as STCs. Ask whether the installer is accredited, review product and workmanship warranties, and confirm who will handle grid connection and future support. Make sure the energy estimates explain their assumptions, including your location, roof orientation and shading. Getting several itemised quotes can help, but a licensed installer should confirm that the proposed system suits your home and electrical setup.