A solar payback period is the time needed for electricity-bill savings and export credits to recover the system’s upfront cost. It varies with system size, installation price, eligible incentives such as Small-scale Technology Certificates (STCs), household energy use, feed-in tariff and future electricity rates. Using more of your solar during the day generally improves payback, while a battery can change both the upfront cost and savings calculation. Ask several accredited installers for tailored estimates and check the current rules with the Clean Energy Regulator and your electricity retailer.