A Geothermal generator is a power generator (requires research) that can only be built on top of a steam geyser to convert natural heat into electrical power, providing a constant 3600W. Steam geysers are randomly generated per map, sometimes close to each other, others scattered towards the edges or center. Colonies are often seen built in their proximity from early days for future benefit.
The Geothermal generator can be built indoors, but this causes heat build up and eventually may catch fire. A prevention method is to leave an open path towards outside or intentionally unroof one tile. Vents can be used to pipe the heat into other rooms. An open door will also release some of the heat from its room. However, in cold biomes, the increased temperature becomes beneficial as heat is needed instead. The amount of heat it provides is only a little more than a normal heater.
Geothermal generators have very low beauty score and should have their own room if placed indoors.