Compare each quote using the same details: system size, panel and inverter brands, estimated annual generation, total price, and whether GST, installation and grid-connection costs are included. Check how any Small-scale Technology Certificates (STCs) have been applied, plus the battery’s usable capacity and expected warranty terms if one is included. Look for separate product and workmanship warranties, the installer’s accreditation, payment schedule and after-sales support. Ask the installer to explain assumptions behind the generation estimate, and check the final contract carefully before signing.