From NPR News: Who’s In Charge? Getting Western States To Agree On Sharing Renewable Energy

So, “storing excess energy generated by solar and wind is expensive”? How are they doing that?

Is the excess energy used, say, for desalination? And then used to pump that water up into water towers? Desalined and purified water is a commodity in itself. And releasing stored water from high tanks, you could put energy back into the grid as well, gravity helping it turn turbines (hydroelectric).