When selecting a small wind turbine, there are a few things you need to know before bolting one up to your house. The lower the voltage system you are running, the less amps the wind turbine will pump out. There are a TON of folks on ebay swearing by their PMA turbines being the most powerful, but in reality, there all pretty much the same. Though some may have a better design than others, the overall output may be the same.
Let's use a battery charging system for example. Most commonly used system voltages are 12, 24, 36, & 48v. Most home experimenters are using 12v systems because of 12v being the most affordable and parts can be purchased from pretty much anywhere from Walmart to your local auto parts store. If you basic OHMS LAW, a 500w turbine will clearly not put out 500w if used on a 12v system.
If you do the ohms law math - volts x amps = watts, you will see a way different number.
Unless you live inside of a permanent hurricane, your normal average wind-speed, blade size/length & pitch, and number of blades will determine your overall RPM of your turbine.
Lets say you have average wind speed of 12mph. You are using a 4-500 advertised watt PMA turbine with 35" blades in 3 blade configuration. You are charging 12v batteries. You are only going to see up to 60 watts (which will charge a battery) and may be inefficient to charge larger battery banks. If wind is your choice of alternative energy, you may want to go with a higher voltage system, or multiple low voltage turbines.
A low wind PMA that hits 12v at about 130 rpm, running a 35"x3 blade configuration yields approx 5-10 amps max. Cut in speed is about 2mph. If the blades config was 24"x3, the cut in speed would be higher - maybe 6-7mph, but output would be about the same if not a little less.
Im not the greatest writer, so I hope this sheds some light on the subject. Im happy to answer any questions.
