3 ms·

But how expensive would be to dig a, I don't know, 1000 by 6 feet hole in the ground? I have no idea of an equivalent gravity battery...

• thfuran 2y ago
  The average US household uses about 10,000 kwhr per year. That's roughly equivalent to the gravitational energy of dropping ten tons down a 200 mile hole.
  • EGreg 2y ago
    The battery doesn’t have to hold the entire year’s energy — come on :-P
    • mft_ 2y ago
      Indeed, but to store (let's say) half a day's energy, then (based on the previous calculation) it would presumably need ten tons dropping down a hole 0.274 miles, or 441 metres, deep?