If you are looking for a small or mid-sized wind turbine, Windustry recommends selecting a model that has been certified by the Small Wind Certification Council:
"A certified machine enables consumer comparison of the wide variety of wind turbine products on the market. Funding agencies and utilities will gain greater confidence that distributed wind turbines installed with public assistance have been tested for safety, function, performance, and durability and meet requirements of consensus standards. Certification can help prevent unethical marketing and false claims, thereby ensuring consumer protection and industry credibility."
Additionally, new rules in 2015 by the IRS require that a certified wind turbine is used in order to be eligible for certain tax credits. Read more about the IRS rule here.