Is Your Site Windy Enough?
Wind speed, tower height and space: the three tests every site must pass.
See Wind MapsThe wind at your property decides almost everything about a home wind turbine: how big it should be, how tall the tower must be and whether it is worth doing at all. Here is how to size up your site before you spend money.
Step 1: Estimate Your Average Wind Speed
The DOE’s Small Wind Handbook sets clear thresholds. A grid-connected system is generally practical where the average annual wind speed is at least 10 mph; an off-grid hybrid system can make sense at about 9 mph. These are averages over a year at hub height, not gusts you notice on a blustery afternoon.
| Source | What it tells you | Limits |
|---|---|---|
| Wind resource maps | A first look at the average wind in your region | Broad scale; local hills and trees change the picture |
| Nearby airport or weather station data | Long-term averages and seasonal patterns | Measured at one height on open ground that may differ from yours |
| On-site measurement | The wind at your actual location and height | Takes time; best done over a full year |
| Local clues | Wind-shaped trees, nearby turbines, other owners’ results | Useful hints, not numbers |
The WINDExchange wind resource maps are a good first stop. The handbook notes that maps at 30 to 40 meters are the most useful for small wind, because they are closest to typical home tower heights.
Step 2: Get Above the Obstacles
Trees and buildings break smooth wind into turbulence that cuts output and wears out parts. The rule of thumb in the DOE handbook is that the bottom of the rotor should be at least 30 feet above any obstacle within 300 feet of the tower; elsewhere it uses a 500-foot radius, so more clearance is better. Remember trees keep growing.
Place the turbine upwind of buildings and trees in the prevailing wind direction. On a guyed tower, the guy anchors spread out to between one-half and three-quarters of the tower height, so plan that footprint too.
Step 3: Check Your Space and Neighbors
- Plan for at least one acre, according to the DOE handbook.
- Find out your zoning height limit; the handbook notes many codes cap structures at 35 feet.
- Measure setbacks from property lines, roads and power lines.
- Talk to neighbors early about the view and sound.
- Confirm access for a crane or gin pole on installation day.
Step 4: Know How Much Power You Use
Pull twelve months of electric bills and total your kilowatt-hours. A smaller turbine can trim a bill; covering most of a typical home’s use takes a larger machine and a better site. Cutting waste first — insulation, efficient appliances, LED lighting — lets a smaller home wind turbine do more of the job.
Siting Questions
Can I use the wind reading from my local airport?
Airport data is a starting point, but it is measured at a fixed height on open ground that may not match your site. Treat it as a rough guide, and look at wind maps for heights closer to your planned hub.
How tall should the tower be?
Tall enough that the bottom of the rotor sits at least 30 feet above anything within 300 feet. In practice that often means a tower considerably taller than local zoning allows by default, which is why many owners apply for a variance.
Is one acre really necessary?
The DOE suggests at least an acre for a home wind system. You need room for the tower, setbacks from property lines and buildings, and guy-wire anchors on a guyed tower.
Use the Federal Small Wind Tools
WINDExchange, from the U.S. Department of Energy, has wind maps, the Small Wind Handbook and state resources to help you judge your site.
Open the Wind Resource Maps