Final answer:
Solar panels feed back to an electrical grid by using an inverter to convert the direct current (DC) output of the solar cells to alternating current (AC) that is required for most household appliances.
Step-by-step explanation:
The output of solar cells is direct current (DC), which is not suitable for most household appliances that require alternating current (AC) voltage. To feed the solar energy back to the electrical grid, an inverter is used to convert the DC to AC. This device allows any extra output from the solar panels to be passed on to the outside electrical grid for sale to the utility.