Coal-fired power plants, lose about two thirds of the energy in the coal (meaning only about 1/3 of the energy in the coal ends up as electricity). The electricity then leaves the power plant, and around 12 percent is considered "line loss" due to resistence and inefficient systems(making transmission efficiency around 88 percent). So the end-to-end efficiency if coal-fired power is probably 0.33 x 0.88 = 0.29 or 29 percent efficiency. This does not take into consideration that a coal fired plant, uses millions of gallons of water and also creates long term carbon and coal sludge waste that has a reciepie of toxic or harmful chemicals that impact ground and water supply. The impact of the coal "emissions" is well known as a leading cause of pollution in the world.
By contrast, a typical wind turbine is about 30% efficient in converting the energy from the wind, into electricity, and turbines placed near the "user", typically show a 1%, maximum 2% line loss. Wind uses no water, and has no emissions, or sludge. So we might say that wind energy isas efficient as coal production, which much less financial cost, or negative impacts upon health or the environment.One of the key factors is that wind turbines can be placed locally, or near the location of consumption. Industrial plants, malls, hospitals, and universities are learning that turbines can be sized, so that one can produce the electrical needs for a dormitory, or an assembly line, or kitchen.
Therefore, because of the "close proximity" there is very little line "resistance" loss, increasing efficiency. Battery packs, or systems can be installed so that the turbines always keep a one or two day supply of power charged up into the back up battery system in the event of a "no wind" period. Furthermore a master switch, and put a building "back" on the grid, if there is an extended "no wind" situation. But, that is rare and another system we like, is to put in a hybrid system that includes wind power, PV solar panels, and solar water heating. The three together can bring many buildings to a "net zero" status. (Meaning, they produce as much energy as the building needs, therefore eliminating electric bills.)