Example of how much you'd have to "overbuild". Look at example temperature and incoming solar radiation around january - february. Graphs 1 and 3 [1]. And that's for Vantaa in the far south of Finland :)
Same reasoning applies to wind, though, Its price is dropping nearly as fast as PV.
But chemical battery prices are also dropping as quickly.
At present the BESS (battery energy storage system) industry is (to a first approximation) a sideline for vehicle battery makers.
Relaxing engineering constraints imposed by vehicle use[1] means BESS prices can drop further. This is happening as the BESS industry splits off from vehicle batteries.
Add vehicle battery swapping like Ample's[2] to an urban BESS, you have two businesses in one, that can follow supply availability exactly.
1. Structural strength, vibration resistance, performance at extreme high and low temperatures, high mass energy density, high power/mass ratio, tolerance for overdischarge being the obvious constraints that can be relaxed a bit.
See this video which suggests somewhere in the region of 5x overbuild of renewables being the least cost option.
https://news.ycombinator.com/item?id=33464463