Residential Wind Power Facts
Notice that a 20% increase in wind speed from 10 to 12 mph yields a 66% increase in
Wind speeds are typically highest during winter months and taper off throughout the
summer. To illustrate this, you can view a monthly kWh production chart kept by the
owner of a Skystream 3.7.
What are the requirements for a viable wind powered system?
1. Zoning laws that enable the installation of wind powered systems. The first place to
start is your town's building department. Here's a link to a short but instructive zoning
overview for small wind turbines. (PDF)
2. Sufficient land and open space. The land requirement will depend on zoning laws
but the suggested minimum is one acre. As far as open space goes, the tower and
generator should be sited in an area free of obstructions for 500 feet around the
3. Wind - the minimum requirement is 10 mph average annual wind speed. As the
monthly energy chart above shows, a seemingly insignificant increase in wind speed
pays big dividends. The most cost effective method to increase wind speed is to
increase tower height.
Find your local wind speed in 2 easy steps
1. Click on your state (click again to enlarge) on this wind resource map. Look at the
color coded Wind Power Classifications and determine if you live in a Class 2 or better
area. If your area is designated Class 1 you should consider solar power instead.
The one drawback to the maps you just viewed is the wind speed measurements
were taken at 50 meters, or 164 feet, and don't accurately reflect the wind speeds at
the top of shorter towers used for home wind generation.
2. A more accurate, though still imperfect solution to this problem can be found at this
table of average wind speeds. This resource lists the wind speeds at elevations closer
to standard tower heights. Choose a city or town closest to your own and look at the
far right column labeled ANN for the annual average wind speed. Your best chance for
meaningful power generation lies in areas where the wind speed exceeds 10 mph.
Wind power production calculator
Once you estimate wind speed it's easy to predict the power output from any size
turbine by using our exclusive Monthly kWh Calculator. The only other piece of
information you'll need is the length (also referred to as diameter) of the generator's
You will find the specs for a variety of turbines on the Turbines and Towers page.
The generator produces wild 3 phase alternating current (AC). The wild AC is rectified
to direct current (DC) and either stored in a battery bank for future use, or sent
through an inverter and modified into appliance friendly AC power for immediate use.
Grid tied wind systems
When the power from the inverter is routed directly into your home's main circuit panel
you have a grid tied system. A grid tied wind system provides electricity to your home
only when there's sufficient wind. On calm windless days your home will rely on the
"grid." Most residential turbines will not produce usable amounts of electricity until the
wind speed exceeds 7 mph.
Battery wind systems
Another option is to route the power directly into a battery bank for current and future
needs. The incorporation of this type of system into your lifestyle is referred to as
"living off the grid." But to ensure that 100% of your power demand is met you must
carefully size the system taking into account wind resources, turbine size, and tower
Hybrid wind power systems
The third option is a combination grid tied system with a battery backup. A battery
backup is good to have when the grid is down or on windless days, but it will add
about a third again as much to the total cost of the system. For this reason, the
majority of wind systems sold are grid tied only.
Some manufacturers make only battery-charging machines, and may offer a variety of
turbine voltages. Others produce machines intended to connect to grid-synchronous
inverters without batteries. One machine by Skystream integrates the inverter with
Wind turbine power ratings
All home wind power generators are assigned a Kw (kilowatt) rating by their
manufacturers. Unfortunately, the peak power "rated at" Kw number assigned to
various wind turbine models is meaningless since there is no accepted, industry wide
standard for measuring a turbine's output. The rating inconsistencies are mainly due
to differing "example" wind speeds used by individual manufacturers to calculate peak
A more accurate approach to estimating the energy output of a turbine at various
wind speeds is to use the chart provided on the manufacturer's website.
The chart on the left illustrates estimated
monthly output in kWh (kilowatt hours)
based on average annual wind speed for
the Whisper 500 by Southwest Windpower.
At average wind speeds of 10 mph you
could expect 300 kwh of energy production.
At average wind speeds of 12 mph the
energy output is around 500 kWh.
The American Wind Energy
Association (AWEA) reports that
the U.S. market for residential
wind power turbines – those
with capacities of 100 kilowatts
(kW) and less – grew 78% in
The largest sector of this market
is residential wind turbines in the
1-10 kilowatt (Kw) range and are
the focus of this article.
The mechanics of a wind turbine
are pretty basic. In most small
wind turbines the rotor
(propeller blades and hub) are
connected directly to a generator