Check that the installer holds current Clean Energy Council accreditation for the relevant solar or battery work, and confirm their licence details in your state or territory. Ask for a written quote covering system design, equipment models, expected performance, installation costs, warranties, monitoring, grid connection and any small-scale technology certificate (STC) arrangements. Also check the installer’s insurance, after-sales support, reviews and references, and make sure you understand who handles approvals and defect claims. The CEC website and your state consumer affairs agency can help you verify credentials before signing.