As stated, the towed generators are best used by those who actually sail steadily. The power generation is quite impressive compared to the wind and solar systems. The most I've heard of in terms of speed loss is less than half a knot. They are the power generation source of choice for trans-oceanic racing and the 'round the world events. The link below may be of some interest to you as i believe it discusses most of the more commonly found ones.
“Scientists are people who build the Brooklyn Bridge and then buy it.”
Wm. F. Buckley, Jr.
Last edited by sailaway21; 12-17-2007 at 12:10 AM.