For example:

The Skystream 3.8 wind generator is rated at 1.8 kW
The Jacobs 31-20 wind generator is rated at 20 kW

A power rating in this case is an instantaneous power output at any given moment - a snapshot in time. And there is no industry standard to compare generators built by one company to another company - because they all use a different wind factor.

Southwest Wind Power (maker of the Skystream) uses a wind speed of 22.3 mph to rate their generator at 1.8kW

Abundant Renewable Energy (maker of ARE442) uses a wind speed of 23 mph to rate their generator at 10kW

Entegrity Wind Systems, Inc. (maker of EW15) uses a wind speed of 25 mph to rate their generator at 50kW

Bergey Windpower Co. (maker of BWC Excel 10kW) uses a wind speed of 29 mph to rate their generator at 10kW

The use of this power rating is not a good indicator for generator comparison. What we need to focus on is the actual energy production of a wind generator. Energy - not power. Power is the instantaneous measurement. Energy is a factor over a period of time, for example, a month.

Most wind generator manufacturers will give an energy production factor (kWh) over a month's time using average local wind speeds (mph). This is the rating we should focus on. And each product will differ depending on local wind conditions.