Windmills will never provide significant amounts of cost-effective electric power to a national grid which has to respond instantly and continuously to variable consumer demand.
Wind power is a mature technology which does not need subsidising but it can not and probably never will compete with gas, oil, or nuclear.
The consumer is subsidising wind power through the provisions of the UK Renewables Obligation (2002).
The reason for the outrageous subsidy is the panic over global warming, whose attribution to man-made carbon dioxide is (at least) simplistic and whose possible consequences are probably distorted and certainly exaggerated.
Why is this idea important?
Public energy policy is being diverted and distorted by emphasis on technologies, such as windpower, that can never provide the required substitute for coal (which is relatively dirty) and gas (which has security issues).
In the short term, nuclear is the only practical answer. In the long term, the money that is being squandered on wind power should be directed into research that has some prospect for success.