Storage at the scale needed to deal with intermittant generation is unsolved. You would be looking at trillions of dollars on top of the costs of actual generation for a large european country. Price per kWh of storage and usage of countries are easily searched figures, multiply them together for a few hundred hours and it is obvious.

That is what makes a majority renewable grid more expensive. Obviously fossil fuels are cheaper ignoring externalities, but assuming you want to get off those and dont have spare hydro capacity what otber choice is there?