What you say makes sense, but the main power source these days is natural gas. The thing is gas plants are pretty cheap to build and keep running, but fuel costs are high.
A plant that costs $500 million to build can burn a $1 billion in fuel per year.
It can make a lot of sense to spend $500 million on the gas plant and $500 million on wind turbines next door. The wind will be intermittent, but if it defers only half the fuel cost you’ve broken even in a year.
Good análisis !