Compute a maximum safe output rating for your turbine using a reasonable methodology, etch it into a nameplate, and fasten it to the turbine. B-)
I doubt anybody will seriously argue that your homebrew turbine is good for more than 100 KW.
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The devil here may be in details - like other laws or (more likely) administrative regulations on how to rate turbines, requirements for certifications, etc. (And watch out for new rulemaking when the executive branch industry regulators and/or the IRS get around to implementing this.)
Does it cover the the other parts of the system (batteries, inverter, etc.)? I'd be inclined to install the bulk of the system with UL-certified stuff and claim those costs, plus materials and any hired labor costs on the homebrew parts, then argue with the tax guys about whether they'll allow it if they decide to audit me. Worst case I'd expect is to have to refund the deduction (plus maybe a late-payment penalty) on the homebrew part. But I'd talk with my tax accountant first.