Home wind turbines have different efficiencies at different wind velocities. Wind turbines are “most” efficient in a wind speed that is about 30 miles per hour. A home wind turbine functioning in a 10 miles per hour wind will have a much lower efficiency.

A good rule of thumb is to measure the average wind velocity where you live (or look it up) and compare this wind velocity to the energy conversion efficiency that the manufacturer specifies. So, if your average wind velocity is 20mph, you can look up how the wind turbine functions at 20 miles per hour. The graph from the manufacturer may also be listed in watts per square meter, in which case you will need to convert.

Once you know the efficiency of your wind turbine, you can go about calculating how much energy you will be producing from your turbine. Lets say that the efficiency of your wind turbine is 20% at 20 miles per hour. You need to use a conversion chart to convert from miles per hour to watts/square meter. Or, you can use the formula .0006*V^3 to find the watts per square meter, where velocity is measured in meters per second. A wind velocity of 20 miles per hour is equal to 600 watts per square meter.

The next step is calculate the “area” of your wind turbine. This can be done using the length of one of the turbine blades as the radius of a circle and then calculating for the area that circle. Once, you know the area of your turbine in square meters, you can find out how many watts it can produce by multiplying the watts per square meter, by the area. Divide this number by 1000, to convert to kilowatts. Then multiply by the number of hours in a month (720) in order to convert to kilowatt hours.

The number of kilowatt hours the wind turbine produces in a month is the total amount of energy you will produce each month. If you plan on storing the energy in batteries, you may lose some energy. The conversion rate for storing energy in lead acid batteries is about 84%. Therefore, you can multiply your total energy produced by 84% to get the “effective energy.”