So there's three things here: upfront cost, running costs, and decommissioning costs. The running costs of renewable generation are nonzero even if the fuel is

So there's three things here: upfront cost, running costs, and decommissioning costs. The running costs of renewable generation are nonzero even if the fuel is free, as there's considerable maintenance cost. The long run cost - and so the decision whether to build fossil or renewable - has to take all three into account.