You have to build and maintain the storage.
Even if the electricity is free you’ll have to replace your battery once in a while and at current prices that is ludicrously expensive.
It’s cheaper to pay an already built fossil fuel plant to idle with spare capacity.
Give it a few years for battery technology and it may look different.
North Scandinavia.
Most of the electricity here is hydroelectric that has been built many years ago so the power plants are paid off.
The price during summer is very low. In the winter especially the cold months is much higher with Dec-Feb being the peak.
The determining factor is still the capex for storing it. At $50 it makes no sense. At $0.2 it makes sense in some places. I don’t know which assumption is correct, I expect to be wrong in 50% of the cases when I argue on the internet.