There are plenty of places where rooftop solar is at grid parity. We are approaching a time when stored solar electricity will be the cheapest power available even at night. Back in 2012, I estimated the battery price that would allow 24/7 solar to be as cheap as coal/nuclear electricity. I figured that stored solar would be in range of grid parity when batteries were ~$250 per kWh. In 2013, the EIA estimated that we would reach that price point in 2040.

The future is here early. Tesla and GM/LG are quoting prices from $140 to $190 per kWh. I suspect that if we tried to roll out a lot of grid-scale batteries, the additional demand would drive up the price (if only due to lithium supply problems). That being said, if you can do it with lithium, it’s doable with other chemistry. The constraints for stationary grid batteries are different than for vehicle batteries. Size and mass are less critical than price, for instance.

When long term energy scarcity is not a problem, I feel pretty optimistic about a lot of things.