In order to determine whether a home wind farm is a good investment, the home owner should perform a basic analysis. First, determine whether a windmill can meet the home's energy needs.
- Do not rely on the manufacturer's stated output of the windmill; this usually assumes much higher wind velocities than will realistically be attained.
A rough formula for determining the output of a windmill is Output = 0.01328*D2*V3, where D is equal to the blade diameter in feet and V is the average wind velocity in feet per second. This equation returns the expected power output per year in kilowatt hours.
- Next, determine the home's annual usage of electricity. This can easily be estimated by multiplying one month's electricity bill, or otherwise by adding up a previous year's bills if those are available.
- If the windmill is expected to power an entire house, divide the home's usage by the output of a single windmill to determine the number of windmills required.
Once the number of windmills required has been decided, determine whether windmills are more cost effective than simply tapping into the power grid. Many people are installing windmills for reasons other than monetary savings (environmental concerns, for instance, or powering a remote home). However, it is still useful to consider the costs. To determine how long it will take for a windmill to pay for itself, divide the total price of the windmill, including installation and estimated maintenance, by the price of electricity per kWH. Then simply divide this value by the yearly output of the windmill. This will show how long in years it would take for the windmill to pay for itself.
Some other factors may make this calculation more complicated, however. Several countries and areas provide generous subsidies, such as tax credits, for installing wind mills, which lowers the time it takes for a wind turbine to pay for itself. Additionally, if the wind mill is generating more electricity than the home is using, the electric company is in many cases required to pay for the electricity the mill sends back into the grid.
Another idea to consider is collaborating with neighbors to construct a small wind farm with multiple windmills. This may reduce the cost that each person must pay if the total cost is shared among neighbors (for instance, purchasing three windmills for four neighbors).