= Battery Cost =

Batteries for diurnal electric grid levelling are a Dumb Idea.

|| Battery Type	    || Cost per Wh || Wh/kg || Joules/g || Wh/liter ||
|| Lead-acid	    || $0.17       || 41    || 146      || 100      ||
|| Lithium-ion      || $0.47       || 128   || 460      || 230      ||
|| Water, 1 km head || tiny        || 2.7   || 9.8      || 2.7      ||

(from http://www.allaboutbatteries.com/Battery-Energy.html)

Norway has [[ http://norwegen.ahk.de/fileadmin/ahk_norwegen/Dokumente/Presentasjoner/wasserkraft/Design_of_Future_Pumped_Storage_CEDREN_Killingtveit.pdf | 84 TWh ]] of reservoirs that can be converted to pumped hydro.
Conversion would cost a dollar a watt - peaking 50 gigawatts would cost $50B. For long term storage, that is $0.0006 per Wh.
The chart above does not give lifetimes, but reservoirs last a century, and batteries last from 1 to 5 years.

Batteries are good for portable devices, marginally so for data center emergency power (until the generator starts),
execrably lousy for diurnal or seasonal grid load levelling.  Reservoirs rarely catch fire, explode, or emit toxic chemicals.