Although there are many design variations, the three-bladed horizontal axis wind turbine has emerged as the dominant configuration for most commercially-available SWTs. Within this design there are a number of approaches that vary from one manufacturer to another, including heavy versus light construction, and induction generators versus permanent magnet alternators.

Exhibit ES-1 provides an overview of typical characteristics, costs and performance of four generic SWTs modeled using RETScreen™ software at a capacity factor of 20%. The results indicate that SWT energy production costs are generally not able to compete with retail grid electricity. Even for the larger end of the SWT range, electricity costs are roughly double that of current residential rates.