The wired.com article says: > assuming energy transfers are 100 percent efficient—which they aren't. A startup doing a large scale version of this idea using

The wired.com article says: > assuming energy transfers are 100 percent efficient—which they aren't. A startup doing a large scale version of this idea using commercial tower cranes claims 85% efficiency, but take that with a grain of salt: > The round-trip efficiency of the system, which is the amount of energy recovered for every unit of energy used to lift the blocks, is about 85%—comparable to lithium-ion batteries which offer up to 90%. https://qz.com/1355672/stacking-concrete-blocks-is-a-surprisingly-efficient-way-to-store-energy/ https://qz.com/1355672/stacking-concrete-blocks-is-a-surpris... Of course, the gold standard way of doing this is with pumped hydro, hovers around 80% efficient. > The round-trip energy efficiency of PSH varies between 70%–80%, with some sources claiming up to 87%. https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricity https://en.wikipedia.org/wiki/Pumped-storage_hydroelectricit...