Comment by frafra

Cost != price/value. You can produce energy cheaply at noon, but it has little value compared to electricity produced at 18:00. The higher the share of renewables in the electricity mix, the more storage is needed, and it grows faster than linearly. You can also not stock electricity in advance for months in northern areas. There are a lot of factors to keep into account, and the cost of electricity production is often a minor one, when considering the total price.