eli5: If we’re all sitting above the magma and heat in Earth’s mantle, what are the barriers to tapping that heat in each municipality to provide local affordable electricity?
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As others have pointed out, for most places where people live, the Earth’s crust is quite thick. [About 30km / 18 miles](https://pubs.usgs.gov/gip/dynamic/inside.html) and digging really, really deep is really, really expensive.
Let’s take the deepest hole ever dug as an example: The Kora Superdeep Borehole, which was an experiment essentially to see how deep a hole could be dug. The hole is about 9 inches across, and 12km / 8miles deep (so not even half way to Earth’s mantle in most inhabited places). [This hole took nearly 20 years to dig and cost $100 million](https://www.uu.edu/dept/physics/scienceguys/2003Apr.cfm#:~:text=The%20deepest%20hole%20by%20far,7km%20(about%2023%2C000ft).)
And while the bottom of that 8 mile hole is well above boiling (190C / 370F), it’s not nearly hot enough to push the steam 8 miles to the surface .
In the end, it’s just much cheaper and easier to dig 1-2 miles deep for oil, natural gas, and coal and burn that for energy.
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