There are three main advantages to using geothermal energy.
It can be used directly. A person building a new house can use geothermal energy to heat and cool the house. This means they do not have to rely on electricity, gas, or other external sources of power.
It is cheap to run once the equipment needed to tap it is installed. Once a geothermal plant is built, the running costs are very low. The fuel is, essentially, free.
It is not a polluting fossil fuel. By using geothermal energy, we reduce our reliance on fossil fuels. This means that we do not contribute to air pollution and to climate change.