The length of time will vary from project to project, but wind farms can be brought on-stream faster than most other types of power-generating facilities - for example, natural gas power plants, which can take two to three years or more to develop. The permitting process for wind is less complex because wind energy does not have the same environmental impact as fossil-fueled power generators. Wind energy produces no emissions and no solid waste by-products. The length of construction will depend primarily upon the number of turbines to be erected, the terrain and prevailing weather conditions. In some cases, this can all be accomplished within nine to 18 months.