Hacker News Reader

Yeah, that doesn't seem very efficient. I see why this works at larger scales, such as water reservoirs and such, but there's no way this would be worth the cost to install in one's backyard. Especially when the price of equivalent battery-backup systems are only a few thousand dollars.

Which is comparable to 10 kg of lithium-ion batteries - not terrible efficient.

You would have to factor the efficiency motors that raise the weights, and the generator that lowers them to get a more accurate estimate.

That's why I used a kilometer. There's little need for an accurate estimate, capacity for such a system is very expensive, either in dealing with huge masses or huge distances.

By way of comparison, a thousand dollars of lead acid batteries would have more capacity (and despite the issues with lead, such batteries are quite recyclable...).