[StreamBright]

You cannot talk about energy like that. What is the chance that 1 GWH is going to be produced? With a nuclear power plant you can have guaranteed energy, with renewables there is a chance that you get energy. You continously need to balance consumption and production. You can only control non-renewables. This is why building wind farms require the same amount of production is built using gas turbines for the worst case scenario. The £50/GWh vs £90/GWh is for the happy path best case scenario. I hope it makes sense.

[sideshowb]

update: the £50/MWh and £90/MWh are both commercial bids that will have factored in probability of generation to the best of the bidders ability. the companies making them will fail if they go hugely wrong. (though in the nuclear case taxpayer might be left with cleanup)

You are correct that the non-constant nature of wind means you need to cost in some storage, or transport via the grid (generally it'll be windy someplace or other). But probability of generation is not the issue.

[sideshowb]

is the £50 not based on annual average days with sufficient wind to generate (which I presume has fairly low uncertainty, though if it's not generating when you want then either storage or transport is needed)