But prices for lithium-ion batteries have fallen fast—by almost half just since 2014. Electric cars are largely responsible, increasing demand and requiring a new scale of manufacturing for the same battery cells used in grid storage. California is mandating that its utilities begin testing batteries by adding more than 1.32 gigawatts by 2020. For context, consider this: In 2016, the global market for storage was less than a gigawatt.

Source: Tesla’s Battery Revolution Just Reached Critical Mass – Bloomberg