As far as I'm aware, in places with fixed costs, the fixed costs simply pay for the infrastructure, whereas the usage costs go towards running the base power st

As far as I'm aware, in places with fixed costs, the fixed costs simply pay for the infrastructure, whereas the usage costs go towards running the base power station. However my point is that the base power station costs the same to run regardless of usage. If some places already do have a properly priced power system then what I described wouldn't happen, but I also have trouble understanding how intermittent power could compete in a system where base power is essentially free.