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I think the confusion is that the $103/kWh is the capital cost to build the storage rather than the operating cost to actually recover a kWh of energy. So to pr

I think the confusion is that the $103/kWh is the capital cost to build the storage rather than the operating cost to actually recover a kWh of energy. So to provide 10kW for 10 hours (for instance, overnight storage for a large house), they'd need a 100kWh system at a cost of ~$10,000, where they're claiming that a pumped hydro system would cost 20% more. The benefit of course to pumped hydro is that you can have hundreds or thousands of MW in storage. These units would be consistent with other reporting for grid-scale battery systems costing ~$250/kWh to construct: http://cleantechnica.com/2013/12/18/utility-scale-battery-storage-costs-dropping/ http://cleantechnica.com/2013/12/18/utility-scale-battery-st... As for operating costs, I'm assuming that the nameplate storage capacity is the output. So if you have a 100kWh system with ~60% throughput efficiency, you'd need 160kWh of input at your standard energy rates and then the energy coming out would be 'free' -- of course there'd be costs for maintenance and depreciation too though.

gonzo 12y ago
> So if you have a 100kWh system with ~60% throughput efficiency, you'd need 160kWh of input at your standard energy rates and then the energy coming out would be 'free' I think the idea is that this is storage for renewables. As such, you wouldn't need more "input at your standard energy rates" than what it might take to charge the system for overnight use.
- mikeyouse 12y ago
  Right, I guess I was getting at the 'cost' of energy would be he opportunity cost of not selling it back to the grid which is typically the retail price in areas with net metering. Although in off-the-grid situations, you're right that there wouldn't be any incremental cost to charging the storage.
jjoonathan 12y ago
That makes much more sense. My unstated assumption was that a decimal place had been forgotten -- thanks for doing my homework for me and clearing things up :)

gonzo 12y ago

> So if you have a 100kWh system with ~60% throughput efficiency, you'd need 160kWh of input at your standard energy rates and then the energy coming out would be 'free' I think the idea is that this is storage for renewables. As such, you wouldn't need more "input at your standard energy rates" than what it might take to charge the system for overnight use.

mikeyouse 12y ago
Right, I guess I was getting at the 'cost' of energy would be he opportunity cost of not selling it back to the grid which is typically the retail price in areas with net metering. Although in off-the-grid situations, you're right that there wouldn't be any incremental cost to charging the storage.

jjoonathan 12y ago

That makes much more sense. My unstated assumption was that a decimal place had been forgotten -- thanks for doing my homework for me and clearing things up :)