A wind turbine in a calm spot is the most expensive paperweight you can own.
Before you spend a single euro on a turbine, you need to know what's actually blowing where you live. Not what the regional weather map says. Not what your gut tells you on a windy afternoon. The real, average wind at the spot you'd mount the turbine.
Here's how to find out.
What You're Measuring
Two things matter most.
Wind speed. How fast the air is moving. Measured in metres per second (m/s) or miles per hour (mph). 5 m/s is about 11 mph. A gentle breeze that ruffles leaves is around 3 m/s. A stiff wind that bends small trees is around 10 m/s.
Wind direction. Where the wind is coming from. For a horizontal axis turbine, this matters a lot. The turbine has to face the wind, and if the direction shifts constantly, the turbine wastes time chasing it. For a vertical axis turbine, direction matters less. The egg-beater shape catches wind from any side.
For both, you want consistency. A site with steady 5 m/s wind beats one with bursts of 8 m/s and long calms in between.
How To Measure It
The cheap way: buy a small anemometer (the spinning-cup wind-speed meter) for around a hundred euros. Mount it on a temporary pole at the height you'd put the turbine. Let it record for at least three months. A full year is much better. You'll get the average wind speed and the patterns across seasons.
The lazy way: check government wind maps. Most countries publish wind atlases that show average wind speed by region. These are accurate at the regional level but can be off by a lot at a specific site. Use them to decide whether it's worth measuring further.
The free way: ask anyone who's lived nearby for a long time. Local knowledge is surprisingly accurate. "The wind always rips down that valley in winter." That's the kind of thing official maps miss.
What Affects The Wind At Your Site
Three things change the wind right where your turbine would stand.
Location. Coastal sites get strong, steady wind off the water. Open plains get clean, untroubled airflow. Hilltops catch wind that gets squeezed and accelerated as it rises over the slope. All of these are good.
Sheltered valleys are bad. Urban areas are messy. Forested areas eat the wind for breakfast.
Elevation. Higher means faster, smoother wind. Wind near the ground is slowed down by friction with everything underneath. Every metre of extra height matters. Modern turbines keep getting taller for exactly this reason.
A small turbine on a tall tower often beats a big turbine on a short one.
Obstacles. Trees, buildings, fences. Anything within about 150 metres of your site can mess with the airflow. The rule of thumb: the turbine should be at least 10 metres above the tallest obstacle within 150 metres.
A turbine sitting behind a tall hedge or below a row of trees won't perform.
The Magic Number
For most home turbines, the magic number is 5 metres per second average annual wind speed. That's around 11 mph.
Above 5 m/s, a turbine can pay back its cost in a reasonable time, maybe 10 years for a quality system.
Between 4 and 5 m/s, it's borderline. You might still make it work if electricity in your area is expensive and your turbine is cheap.
Below 4 m/s, just don't. Get solar panels instead. They work everywhere.
Modern wind turbines start generating at around 3 m/s, which is roughly walking pace. But "starts generating" is different from "generates enough to be worth it". You need real, sustained wind, not occasional gusts.
DIY Or Hire A Pro?
For a rough check, DIY is fine. Buy an anemometer. Watch the data for a few months. Decide if it's promising.
For a real investment (a turbine costing thousands of euros), hire a professional. They'll do a proper site assessment with calibrated instruments, computer wind modelling, and a written report. The cost is a few hundred to a couple thousand euros, but it's worth it before spending 10x that on a turbine that might not perform.
→ Read more about turbine sizing
→ Are home wind turbines worth it?
→ What does a wind system cost?
→ Use the yearly kWh calculator to estimate your needs.
The wind is free. Catching it isn't. Knowing your site is the first step in deciding whether wind power makes sense for you.
