The potential shortage would happen during a cold spell, when people in housing with poor heating start using small electrical heaters in large numbers. This t

The potential shortage would happen during a cold spell, when people in housing with poor heating start using small electrical heaters in large numbers. This tends to happen in neighboring countries at the same time, so the amount of electricity available for import is low at those times. The negative prices that you quote are very special cases due to wind conditions. The wind doesn't always blow when it is unusually cold. Also, the power lines used for import have limited capacity, and there has been underinvestment there as well.