Electricity prices go up when you have access to customers who are willing to pay more. If grid connections to other regions are limited, people in regions with a lot of cheap generation (such as Norway) pay low prices. But if you add grid connections without increasing generation capacity, prices start equalizing between regions, as every power company tries to sell to the highest bidder.
Norway could power itself fully with domestic hydro. But it chose not to, as the power companies make more money by importing foreign power when it's cheap and exporting hydro when it's not.
Norway could power itself fully with domestic hydro. But it chose not to, as the power companies make more money by importing foreign power when it's cheap and exporting hydro when it's not.