Changes

Wind turbines are not very efficient. That's why you always see such large horizontal machines in the countryside (plus of course their utility scale). The best ones have an efficiency of around 35-47% in an ideal wind. According to Betz's law, no turbine can capture more than 16/27 (59.3%) of the kinetic energy in wind. Practical utility-scale wind turbines achieve at peak 75% to 80% of the Betz limit.

<ref>https://en.wikipedia.org/wiki/Betz%27_law</ref>

Vertical turbines are less efficient than horizontal ones, around 30%. In a design with a diameter of 2-3 m (6-9 ft) you can expect a maximum output of around 2.5 kW (3.35 hp). Small (or “residential”) wind energy systems may be suitable for boats. They range from 400 watts to 500 kilowatts.

== Cost ==

Small vertical turbines cost in the range of USD $5,000 to 10,000.