How this capacity factor calculator works
The capacity factor is the single number that tells you how hard a power plant works. It is central to comparing technologies, to every levelized-cost calculation and to sanity-checking production data. The calculator works in three directions:
- Capacity factor from energy: enter nameplate capacity and the energy produced over a period;
- Energy from capacity factor: estimate the annual output of a planned plant;
- Capacity needed: how many MW are required to deliver a target amount of energy at a given capacity factor (for example, how much solar is needed to produce 1 TWh).
Periods can be a year, leap year, quarter, month, week, day or a custom number of hours, and units are converted automatically between kW/MW/GW and kWh/MWh/GWh/TWh. The result is compared against typical ranges for 14 technologies.
The formula
E = P × T × CF (energy from capacity factor) P = E / (T × CF) (capacity for an energy target) Full-load hours = CF × T Average power = E / T
T is the number of hours in the period (8,760 for a normal year). Use net energy delivered to the grid and the same basis for capacity (for solar, normally AC inverter capacity).
Worked example: a 50 MW wind farm
The default case is a 50 MW wind farm that delivered 140,000 MWh in a year:
- CF = 140,000 / (50 × 8,760) = 140,000 / 438,000 = 32.0%
- full-load hours = 0.32 × 8,760 ≈ 2,800 hours
- average output = 140,000 / 8,760 ≈ 16 MW
32% sits comfortably within the typical 20–45% range for onshore wind. Other presets show the spread: a 6 kW rooftop PV system making 7,300 kWh works out at about 14%; a 1 GW nuclear unit at 92% generates about 8.1 TWh a year; and producing 1 TWh from fixed-tilt solar at a 20% capacity factor needs about 570 MW.
How to read the results
- Capacity factor: compare it with the typical range shown for the selected technology. Below the range points to curtailment, outages, a weak resource or an oversized plant; above it may mean an exceptional site, or an error in the data.
- Full-load hours carry the same information as capacity factor, preferred in Germany and in wind-industry reports.
- Average power is useful when matching a generator to a constant load.
- Output while available (optional) divides capacity factor by availability, separating resource and dispatch effects from downtime.
Typical values
| Technology | Typical capacity factor | Main limiting factor |
|---|---|---|
| Nuclear | 80–93% | refuelling outages |
| Geothermal | 70–90% | constant resource |
| Biomass / biogas | 50–85% | fuel supply, dispatch |
| Gas combined cycle | 45–65% | dispatched on price |
| Coal | 35–65% | declining dispatch |
| Offshore wind | 38–55% | wind resource |
| Hydropower | 30–60% | water availability |
| Onshore wind | 20–45% | wind resource, rotor size |
| Concentrated solar (storage) | 30–55% | storage hours |
| Utility PV, tracking | 20–32% | sunlight, latitude |
| Utility PV, fixed | 12–25% | sunlight, latitude |
| Rooftop PV | 9–20% | orientation, shading |
| Gas/oil peakers | 2–15% | runs only at peaks |
| Battery storage | 8–20% | cycles × duration |
Ranges combine US fleet statistics published by the EIA with global new-build averages from IRENA; individual plants and years vary widely.
Tips
- Use consistent units. The most common error is mixing kW with MWh, which gives results 1,000 times too large or small.
- For solar, state the basis. Capacity factors on DC (panel) capacity are 10–30% lower than on AC (inverter) capacity.
- Compare the same years. Wind and hydro capacity factors vary ±10–15% between good and poor years.
- Feed it into cost models. Capacity factor is the denominator of every LCOE (see the LCOE calculator) and the main output of the wind turbine and solar panel calculators.
Limitations
A capacity factor summarises output, not value: a peaker running 5% of the time can be worth more to the grid than a baseload plant. Typical ranges are broad and vary between countries, years and plant ages. The calculator does not distinguish gross from net generation or account for degradation; enter net energy delivered for the period you care about.
Method & assumptions
Capacity factor CF = E ÷ (Pnameplate × T), where E is net energy delivered in period T (hours). Energy = P × T × CF; required capacity = E ÷ (T × CF). Full-load hours = CF × T. Average power = E ÷ T. Units are converted internally to kW and kWh.
Frequently asked questions
What is capacity factor?
How do you calculate capacity factor?
Which energy source has the highest capacity factor?
What is a good capacity factor for solar?
Is capacity factor the same as efficiency?
What are full-load hours?
Why do gas peaker plants have such low capacity factors?
Sources & references
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