The efficiency of a small wind turbine, as we have so far defined it, may not mean that much.  Unlike engine powered generators which use expensive fuel, the wind doesn't cost anything.  You don't even have to pay a tax to use it, at least not yet.  The efficiency which we have been discussing is governed by the laws of physics and the state of technology.  We can't do much about the first limitation and it would not be unreasonable to conclude that, in a competetive market, manufacturers are likely to embrace and incorporate new technology as it becomes available.  This being the case, our premise that the efficiency of commercially available small wind turbines is likely to be similar is probably a reasonable assumption.  It might therefore be more productive to consider a different type of efficiency - Cost Efficiency.  

Grid connected wind turbines have a number of important purposes.  Providing the owner with a measure of energy self sufficiency is one.  Supporting distributed power generation helps the community at large.  Displacing nonrenewable energy sources and reducing atmospheric CO2 is crucial.  All of these purposes are important, but the reality is that grid connected small wind turbines will probably not see widespread use unless their installed cost is reduced below present levels.  Wind generated electricity from small wind turbines must become more cost effective.  Cost efficiency is unquestionably a matter of importance.  It may also be the most important criteria for comparing small turbines.

Other things being equal, a turbine that can produce electricity for a cost of 8 cents a kilowatt hour would be preferable to one that produced power at a cost of 10 cents a kilowatt hour.  It really doesn't matter which turbine is more effective at extracting energy from the wind.  It doesn't make much sense to pay 20% more for a turbine that only provides a 5% boost in energy efficiency.  If a quality turbine can be be built for a low enough cost, it will make more economic sense even if its efficiency is a bit lower than competing, but more expensive, turbines. 

This is not to say that the Aerostar is any less efficient than other commercially available turbines.  It is not.  What is important is that Aerostar has focused on producing a turbine for a reasonable cost.  Cost reduction was made possible by using finite element stress analysys for the important components.  This analysis has made it possible to build a lighter, stronger turbine for less cost.  Compare the weights of other turbines in the size class of the 6 meter.  The Aerostar is about 2/3 the weight of competitive turbines.  This means a lower cost turbine and a lower cost tower.  Simply adding size and weight to components doesn't mean these components are stronger, they are just heavier.  If we applied this reasoning to aircraft, our primary mode of travel would still be be on boats and trains.