Ugly, noisy, killing birds and a disgrace to the beauty of nature.
Except in Scotland or North of England (where the wind is 24/7/365 ) they are efficient at best 50% of the times. No wind or not enough, no output, too much wind you need to feather the blades or they will detruct the structure by vibrations).
The French RTE the distribution arm of EDF (national elec producer) has all the info day by day, life, hour by hour on their website.
Yesterday 29/06 :
The data on generated power aggregated by sector corresponds to the net power injected into the network.
www.services-rte.com