Solar panels use photovoltaic cells to convert sunlight into direct-current electricity. An inverter changes this into alternating-current electricity that your home can use, while a smart meter measures any surplus sent to the grid. If you have a battery, excess solar can be stored for use later, such as at night. When your system is not producing enough, your home can draw electricity from the grid. The amount you save depends on your system size, energy use, tariff and export arrangements, so compare options with a qualified installer and your electricity retailer.