Having the ability to inspect/service the parts on the tower will be important.
The control system generally will have an anemometer... that will need at least an annual inspection, also the gear box and motor/generator...
The hub where the blades (sails) bolt on should be regularly checked...
If they are still using wood... They should be checked at least quarterly, after their 2nd or 3rd annual, depending on hourly operation...
If you have to pay someone to do that or to get back on line... you reduce the possibility to break even.
If you check with your local weather stations to see the wind velocity history, combine that with the operational perimeters of your system... you can arrive at a close duty cycle. That will give you the most information. DON'T rely only on the information provided by the folks selling it.
How long have they been in this particular business. How likely is it that they will still be in this particular type of business IF there is no longer tax incentives...
Wind generators are kind of fun to work on,:smile: there is not a lot that can go wrong... BUT it is not handy to get to the possible problem, so you have to be prepared to make it handy.
And like most mechanical equipment, you can prevent a lot of repairs by keeping current on your inspections.
The problems with making money selling power back:
You only have a surplus when you are in operation... (wind speed)
You buy power at retail, you sell it back at the LOWEST wholesale rate you utility pays.
Any time there is a problem, your system will be down until it is repaired... Most problems are minor, but you will be the closest person to solve these problems, you will need to be aware how everything in the system should work. :smile:KennyV
Do you have the specifications for the tower and the specs on the instillation?