Hydro isn’t that reliable because in a dry year, you run out of power.

New Zealand has a power shortfall about once every ten years when lake levels drop towards critical levels. In 1992 it was severe enough that nationwide cuts of 15 per cent were needed and the GDP dropped by 0.6%. https://www.nzherald.co.nz/nz/how-we-learned-the-lessons-fro...