Based on the wikipedia article, I think the 1.6bn USD is in 1977 USD. That's going to be roughly 4 times as much by 2017 [1], or 6bn USD, giving about $2,000,00

Based on the wikipedia article, I think the 1.6bn USD is in 1977 USD. That's going to be roughly 4 times as much by 2017 [1], or 6bn USD, giving about $2,000,000/MW capacity at Bath vs $1,900,000/MW for Tesla. Compensating for the fact that only the upper reservoir provides power, storage cost is around $180,000/MWh for Bath vs $475,000/MWh for Tesla. Still significant but at least in the same order of magnitude, and this technology is still improving more rapidly than pumps and turbines. And, the batteries I could put close (or in) cities, potentially saving another 5-20% on transmission losses. I'm now wondering how the operational cost of this will look. Rotating equipment will show wear and I'm assuming Bath has quite some cost on that side. However, that thing has been in operation for over 30 years, and tesla only gives guarantee for 5000 cycles on the powerwall, or about 15 years (assuming 333 cycles a year). If you would actually need to replace the batteries after 15 years then I don't see them beating pumped hydro in the short term, if you can use them for 10'000 cycles with just a loss of capacity, then I think the finances can make a lot of sense. 1: https://www.wolframalpha.com/input/?i=100+USD+in+1977+converted+to+2016 https://www.wolframalpha.com/input/?i=100+USD+in+1977+conver...