Also note that there are cheaper energy storage methods than batteries. Compressed air, pumped water, flywheel and the recently discussed Ares gravity-rail systems have various price points for storage (kWh) and delivery (kW). Here is the ARES discussion:

https://news.ycombinator.com/item?id=11595195

I agree storage (if required) and environmental impact should both be considered when comparing different energy options.