Sizing Grid Connected Systems

The size, or generating capacity, of a wind turbine for a particular installation depends on the amount of power needed and on the wind conditions at the site. It is unrealistic to assume that all your energy needs can be met economically by wind energy alone. As a general rule, a wind system should be sized to supply 25% to 75% off your energy requirements. Most residential applications require a machine capacity of between 1 and 10 kW. Farm use requires 10 to 50 kW and commercial/small industrial uses typically require 20 kW or larger.

Because most buildings are connected to a utility line, many wind turbine owners have opted to interconnect their systems. In effect, they use the utility as a backup system. Excess electricity from the turbine is automatically fed to the utility and backup power is automatically supplied. While this does not constitute true storage, it provides power on demand at any time, in any amount. The process to obtain approval for interconnection from the utility company can be lengthy and complicated, and requires careful planning. The possibilities for interconnection should be investigated early in the process of researching a wind system.

The variability of your energy consumption and the amount of money you are willing to spend on a wind system should also guide your selection. For example, a user whose consumption is erratic or concentrated during short periods of the day should size a wind turbine differently than a user with a fairly constant energy demand. In the former case, wind turbine size should be a function of off-peak or average energy demand.