Wind turbine manufacturers love to quote nameplate power — 30 kW sounds concrete and sells well. The problem is that a turbine rarely operates at the wind speed for which that power figure was determined. This article shows what happens in practice, based on data from FNC Poland's own test bench and field measurements.
Power curve of the FNC-H30
The FNC-H30 is a horizontal-axis turbine with an in-house-built MAGLEV generator. Key parameters:
Below 4 m/s the turbine barely produces usable energy — the motor mostly overcomes its own resistance. Real production effectively starts around 5–6 m/s and grows roughly with the cube of wind speed until rated power is reached.
It's worth noting that the FNC turbine family covers three horizontal-axis variants — FNC-H20, FNC-H30 and FNC-H40 — differing in rotor diameter and generator power, but built on the same design and the same MAGLEV generator. The choice of variant depends on the facility's consumption profile rather than the available wind — nominal power is matched to demand, mast height to local wind conditions.
Why we run our own test bench
Small wind turbine datasheets on the market are often based on simulations rather than measurements. FNC Poland verifies every batch of MAGLEV generators on a test bench before shipping — checking the actual power curve, part-load efficiency and behaviour under gusts. In-house production of the generator and control electronics (not imported off-the-shelf modules) lets us fine-tune control parameters instead of just quoting datasheet numbers.
This process lets us compare declared rated power against the actual bench-measured curve — differences of a few percent are normal, but some cheaper imported turbines fall short by as much as a dozen percent below their declared figures, especially at partial load in the 6–9 m/s range where turbines in Poland spend most of their operating hours.
Real annual yield — table
The figures below come from measurements on 18 m masts in typical onshore Polish locations (open to moderately built terrain).
| Average annual wind speed (10 m AGL) | FNC-H30 annual yield (estimate) | Capacity factor |
|---|---|---|
| 3.5 m/s | 18,000–24,000 kWh | approx. 8–9% |
| 4.5 m/s | 32,000–40,000 kWh | approx. 13–15% |
| 5.5 m/s | 48,000–58,000 kWh | approx. 19–22% |
| 6.5 m/s | 62,000–75,000 kWh | approx. 25–29% |
| 7.5 m/s | 75,000–88,000 kWh | approx. 30–34% |
For comparison: a well-designed 30 kWp PV system in Poland generates around 27,000–31,000 kWh per year. A wind turbine in a good location can therefore produce 2–3 times more energy from the same installed capacity — provided the wind resource is there.
It's worth noting that the seasonal production pattern is the opposite of solar — a wind turbine produces most energy in autumn and winter (October–March), when average wind speeds in Poland run 20–30% higher than in summer. This seasonal complementarity with PV — not nameplate power alone — is what makes hybrid PV+wind systems worthwhile for farms and businesses with steady year-round demand.
Mast height matters more than you think
Wind speed increases with height — the vertical wind shear profile. In moderately rough terrain, the difference between a 12 m and a 24 m mast is typically 15–25% higher wind speed, which, given the cubic relationship between speed and power, translates into 50–90% more energy per year.
| Mast height | Approximate yield increase vs. 12 m |
|---|---|
| 12 m | baseline |
| 18 m | +25–40% |
| 24 m | +50–90% |
That's why in marginal locations (average speed below 4.5 m/s at 10 m) a 24 m mast often decides whether the whole project is viable — while a 12 m mast can be insufficient even with seemingly decent ground-level wind. In practice, the extra cost of a taller mast (typically 15–25% more than a 12 m version) pays back faster than a simple price comparison would suggest, since the energy gain is disproportionately large.
Who a 20–40 kW turbine makes sense for
In practice, the best financial results come from hybrid systems combining an FNC-H20/H30/H40 turbine with a PV installation — thanks to seasonal and daily complementarity, on-site self-consumption can rise to 70–85%, compared with the typical 40–55% for standalone PV in businesses operating around the clock.
Servicing, lifetime and running costs
The FNC-H30 turbine with a MAGLEV generator has no gearbox, which limits the number of mechanically wearing parts. A standard inspection is carried out once a year and covers mast fixings, blade condition, the yaw system and inverter parameters. Annual maintenance typically costs 1–2% of the investment value, and the designed structural lifetime is 20–25 years. In practice this means that after the payback period the turbine keeps running for another decade or more, producing energy at a marginal cost close to zero — and that period determines the overall profitability of the project.
Who it does NOT make sense for
A single-family house with annual consumption of 3,000–5,000 kWh rarely justifies a 20–40 kW turbine — the capacity is disproportionate to needs, and with weaker wind the payback period stretches out significantly. For single-family homes, photovoltaics — possibly paired with an energy storage system — remains the more sensible choice.
Before deciding, check the actual wind potential of your site and project profitability — see the FNC wind turbine range and estimate your yield with our calculator.
