This simulation used 24GW/120GWh (five hours at average demand) and achieved 98.8% renewable supply at a cost of $95/MWh, including the cost of additional transmission, storage and curtailment.

so they used a large number for storage. However, there is 7GW/33GWh of existing, under construction or financed BESS projects, and according to the study, 10GW/40GWh of storage will allow for 94% renewables, which is pretty bloody good.

But yeah, it would be interesting to see BEV's assisting.