Capacity Factor Calculator Formula
Understand the math behind the capacity factor calculator. Each variable explained with a worked example.
Formulas Used
Capacity Factor
capacity_factor_pct = actual_output_mwh / max_output * 100Maximum Possible Output
max_possible_mwh = max_outputUnused Capacity
unused_capacity_mwh = max_output - actual_output_mwhVariables
| Variable | Description | Default |
|---|---|---|
actual_output_mwh | Actual Energy Output(MWh) | 2500 |
rated_capacity_mw | Rated (Nameplate) Capacity(MW) | 2 |
period_hours | Time Period(hours) | 8760 |
max_output | Derived value= rated_capacity_mw * period_hours | calculated |
How It Works
Power Plant Capacity Factor
The capacity factor measures how much energy a plant actually produces compared to its theoretical maximum if it ran at full power continuously.
Formula
Capacity Factor = Actual Output / (Rated Capacity x Hours) x 100%
Typical capacity factors: Nuclear 90-93%, Natural gas 40-60%, Wind onshore 25-45%, Solar PV 15-30%. Higher factors mean better utilization of installed capacity.
Worked Example
A 2 MW wind turbine produces 2,500 MWh in one year (8,760 hours).
- 01Maximum output = 2 MW x 8,760 hr = 17,520 MWh
- 02Capacity factor = 2,500 / 17,520 x 100 = 14.3%
- 03Unused capacity = 17,520 - 2,500 = 15,020 MWh
Frequently Asked Questions
Why is solar capacity factor so low?
Solar panels only generate power during daylight and output varies with clouds and seasons. A 25% capacity factor means the panels average one quarter of their peak rating.
Does a low capacity factor mean the plant is inefficient?
Not necessarily. Wind and solar have low capacity factors due to weather variability, not mechanical inefficiency. The metric reflects resource availability.
Can capacity factor exceed 100%?
In rare cases, a plant may briefly exceed its nameplate rating under favorable conditions, but sustained capacity factors above 100% are not possible.
Ready to run the numbers?
Open Capacity Factor Calculator