[DonRotolo]

Voltage is only part of what you need to measure. You must also measure current, to calculate POWER. There must be a small load on the generator - maybe a light bulb, maybe just a resistor - and by measuring voltage (V) and current (I), P=V*I (P is in Watts)

(Rememebr that Watts is power, and if your system can generate xx watts, the resistor must be able to handle xx watts or more, or it'll overheat)

Don

PS: you DO realize of course that the amount of fuel being spent to overcome the drag of the wind turbines is far greater than the energy produced by the turbines, right? That's called "efficiency", always less than 100%.