Futurology

The total geothermal power produced within the Earth is around 47 TW, and humans currently average around 21 TW usage, which is actually pretty close. However the Earth is absolutely huge and has billions of years of thermal energy stored in it. I imagine if we massively scaled up geothermal generation we'd slowly deplete the energy near the surface and would have to go deeper, but that would probably be on a timescale of thousands of years.