Energy storage might not be cost effective in Germany as a method of helping the transition to a higher grid penetration of renewable energy, until that penetration level reaches as high as 90%, according to a leading think tank.

In the year that has passed since Germany began offering subsidies for lithium-ion battery systems for residential use, around 4,000 solar-plus-batteries have been installed, the country’s Federal Solar Industry Association (BSW Solar) has announced.