How big a system do I need?
Most small wind turbines have a rating or size based on the maximum electricity they can generate such as 1.8kw or 5kw. But that is not a very useful number for most consumers. Rated output is the peak production at a specific (and usually high) wind speed, and different manufacturers use different wind speeds to determine rated output.
A more useful measure is to determine how much of your power a wind turbine can supply. Any reputable small wind turbine representative will supply you a power curve, showing how much electricity the machine produces at a given wind speed. Use this to estimate how much electricity (kwh) the turbine will produce each month or year at the average wind speed you expect or measure at your site. Match this output with your annual energy consumption. To determine this number, check your monthly bills to come up with the annual total of kilowatt hours of electricity you use.
Once you have determined your annual electricity use, you can decide how much electricity you want to offset with a turbine, based on budget and other considerations. For example, if you want to offset nearly all your electricity use and have determined you have annual usage of 10,000 kilowatt hours, select a turbine that will produce that much power over the course of a year at your average wind speed.