Wind Capacity Factor Calculator

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Wind Farm Analysis

Model capacity factor, generation, and net load factor

Capacity (MW)

Capacity Factor (%)

Availability (%)

Grid Loss Factor (% as decimal e.g. 0.97)

Power Price (£/MWh)

CfD Strike Price (£/MWh)

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42–52%

Offshore Wind CF

25–35%

Onshore Wind CF

£37–73

CfD Strike Prices (AR4–AR6)

Understanding Wind Farm Capacity

Wind farm capacity factor depends on wind resource quality (location, altitude), turbine efficiency (power curve), and availability (downtime). UK offshore wind: 42–52% CF. Onshore: 25–35% CF.

🏠 Wind Farm Capacity Explained

A 100 MW wind farm running at 42% capacity factor produces 42 MW of power on average over a year (equivalent to 100 MW running at 42% power). UK offshore wind achieves 42–52% CF due to stronger, more consistent winds at sea. Onshore wind achieves 25–35% due to terrain and lower average wind speeds. Hornsea One (world's largest offshore farm, 1,218 MW) has achieved ~40% CF, confirming real-world offshore performance.

Wake Effect and Array Efficiency: Wind farms lose 5–10% of potential output to "wake effect"—turbines downwind of others experience reduced wind speed. Modern optimization (larger spacing, optimized layout) minimizes this. Availability factor (% of time turbines are running) is typically 96–98% for offshore, 94–96% for onshore (requires maintenance, repairs).

📊 Wind Capacity & CfD

Weibull Distribution: Wind speed varies seasonally and daily. UK offshore follows Weibull k≈2, c≈9–10 m/s. Power output is proportional to wind speed cubed (P ∝ v³). Small increases in mean wind speed dramatically increase power output. P50/P90 yield assessments account for historical wind variability.

CfD Mechanics: Contracts for Difference guarantee a strike price. If wholesale market price falls below strike, generator receives difference. If price rises above strike, generator pays difference. AR4 (2019) cleared at £37–40/MWh (2012 real) for offshore. Generator takes full market revenue risk above/below strike. Cost to government: strike price minus forecast reference price, multiplied by generation volume.

Net Load Factor: After grid losses (TNUoS transmission charges, balancing costs), net load factor is typically 97–98%. CfD difference revenue = (Strike Price – Reference Price) × Generation MWh. Reference Price is EPEX-based, published daily. Positive payment when market < strike; negative (generator pays back) when market > strike.

Frequently Asked Questions

What is the best capacity factor for offshore wind?

UK offshore wind ranges 42–52% depending on location. North Sea (Hornsea, Dogger Bank) achieve 45–52%. Celtic Sea (offshore Wales) achieve 40–45%. Irish Sea achieve 40–48%. Modern 12–15 MW turbines with larger rotors push CF higher than older 5–8 MW turbines. Industry target: 50%+ CF for new projects.

What causes wind curtailment?

Wind curtailment (forced power reduction) occurs when local grid can't absorb all generation, typically during very windy, low-demand periods. Constraint payments (via Balancing Mechanism) compensate generators. Recent curtailment: 5–7% of UK wind output annually (increasing with wind penetration). Future: batteries and interconnectors will reduce curtailment.

How does wake effect reduce output?

Turbines downwind lose 5–20% of potential output depending on spacing. Optimal spacing: 4–6 rotor diameters between turbines. Modern wind farm designs optimize layout using CFD (computational fluid dynamics). Wake loss is included in P50/P90 yield forecasts (not a hidden cost). Large farms (1,000+ MW) can experience 3–5% overall array efficiency loss.

What is the difference between P50 and P90 yield?

P50 = 50% probability of achieving or exceeding. P90 = 90% confidence of achieving at least (low-side estimate, for debt service). P90 is typically 5–10% lower than P50. Lenders require P90 yield to ensure debt repayment even in weak wind years. Investors value P50 for upside potential.

How are CfD payments calculated?

Annual payment = (Strike Price – Reference Price) × Annual Generation MWh. Strike price is fixed (2012 real pounds, inflation-linked post-2020). Reference Price is daily EPEX price (15-min settlement). Example: 100 MW at 45% CF = 394.2 GWh/year. If strike = £40/MWh, market = £80/MWh, generator pays back: (80–40) × 394.2 = £15.77m/year. If market falls to £20/MWh, generator receives: (40–20) × 394.2 = £7.88m/year.

Wind Capacity Calculator

Wind Farm Analysis

Understanding Wind Farm Capacity

🏠 Wind Farm Capacity Explained

📊 Wind Capacity & CfD

Frequently Asked Questions

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