Klimabedrag.dk

Professor Dieter Helm, an economist from the University of Oxford, told the BBC he doubted a large expansion in offshore wind power was affordable. He said: "Offshore wind is one of the very few things that makes nuclear power look cheap."
The professor makes sense to me, but in reality the case is even worse than he describes. On the BBC website a bar graph of cost per energy source was produced:

I doubt that the subsidies are included in the this graph, but even worse is the the usual missing backup and compensation facilities. Wind is far from constant, it changes all the time, causing the wind power, to vary at the power of 3. Although pitch regulation of the wings can do a good job of compensating somewhat for the poor property of the wind, the electrical output power changes drastically throughout the day. Because the grid needs perfect balance between demand and supply, gas generator power plants are needed to actively compensate for any in-balance. You need approximately the same size of gas generators as as you have installed name plate capacity in wind turbines.
Therefore I produced the graph below, which illustrates a more true cost of "additional" generation by wind turbines.

I have been very modest using old gas turbine. In reality one should use the cost with new gas turbines to add to the cost of wind, in particular when talking expansion of power generation.
You might object: as long as the wind is blowing, we save on gas, coal and nuclear. Wrong, or at least not quite right, because the conventional power generators' efficiency goes down the drain, when they constantly have to change the power output.

Also, wind turbine owners are most often paid for stopping their windmills during low consumption periods where the wind blows too much, and where it is not enough to "switch off" the gas turbines. This brings me to yet another point: there is a limit to how many wind turbines you can run in comparison to the conventional supply. This limit is dependent on many factors, and is way beyond the scope of this response, but fact is that the more windmills, the more difficult and expensive it becomes to run the grid.