What is capacity factor?

Capacity factor = actual energy produced ÷ theoretical maximum if the plant ran at nameplate 24/7. A 100 MW solar farm at 25% capacity factor produces 100 × 8,760 × 0.25 = 219,000 MWh per year.

Why is offshore wind capacity factor higher than onshore?

Ocean winds are stronger and steadier than land winds. Modern offshore turbines hit 45–55% capacity factor; onshore averages 35%.

Why is geothermal capacity factor so high (72%)?

Geothermal is a baseload resource — heat from the earth is constant, so plants run nearly 24/7 minus maintenance. It's one of the most consistent renewables.

How is "homes powered" calculated?

It divides annual kWh by an average household's annual consumption. US EIA RECS 2022 puts the US average at 10,500 kWh — but a single-person apartment uses ~3,000 kWh; an all-electric home with EV charging uses 15,000+.

Where does the CO₂ factor come from?

US EPA eGRID 2022 reports the national average emissions intensity of grid electricity at 0.386 kg CO₂e/kWh. Local grids vary — California is ~0.20; West Virginia is ~0.75. Override the factor with your local utility's number for accurate results.

Renewable Energy Calculator

Convert renewable capacity to annual kWh, homes powered, and avoided CO₂ using EIA capacity factors.

Written by Golam Rabbani, Founder & Lead Engineer

This interactive tool requires JavaScript. Read the formula and worked example below; you can compute the result by hand.

How to use this renewable energy calculator

Pick a renewable source (solar PV, onshore wind, offshore wind, hydro, or geothermal).
Enter the installed nameplate capacity in kW.
Optional: override the capacity factor (defaults from US EIA AEO 2023).
Optional: override the average household kWh (default 10,500 from US EIA RECS 2022).
Optional: override the grid emission factor (default 0.386 kg CO₂/kWh from US EPA eGRID 2022).
Press Calculate to see annual kWh produced, homes powered, and CO₂ avoided.

About this renewable energy calculator

The renewable energy calculator converts an installed renewable capacity into annual energy production using the universal formula: annual kWh = capacity (kW) × 8,760 hours/year × capacity factor. Capacity factor is the fraction of nameplate output a source actually delivers over a year, accounting for nighttime, weather, and maintenance. The result is then divided by average household consumption to get "homes powered" and multiplied by the grid emission factor to get CO₂ avoided.

Example: a 10 kW residential solar PV system at the US EIA average capacity factor of 24.5%. Annual kWh = 10 × 8,760 × 0.245 = 21,462 kWh/year. At 10,500 kWh per US household, that powers ~2.0 homes. At the eGRID 2022 grid average of 0.386 kg CO₂/kWh, CO₂ avoided = 21,462 × 0.386 = 8,284 kg ≈ 8.28 tonnes/year.

Capacity factors are EIA-published 2023 US averages: solar PV 24.5%, onshore wind 34.5%, offshore wind 45%, hydro 40%, geothermal 72%. Your local figure varies — desert solar can hit 30%, coastal wind 50%, run-of-river hydro just 30%. Use the override field for site-specific or non-US data.

FAQ

What is capacity factor?: Capacity factor = actual energy produced ÷ theoretical maximum if the plant ran at nameplate 24/7. A 100 MW solar farm at 25% capacity factor produces 100 × 8,760 × 0.25 = 219,000 MWh per year.
Why is offshore wind capacity factor higher than onshore?: Ocean winds are stronger and steadier than land winds. Modern offshore turbines hit 45–55% capacity factor; onshore averages 35%.
Why is geothermal capacity factor so high (72%)?: Geothermal is a baseload resource — heat from the earth is constant, so plants run nearly 24/7 minus maintenance. It's one of the most consistent renewables.
How is "homes powered" calculated?: It divides annual kWh by an average household's annual consumption. US EIA RECS 2022 puts the US average at 10,500 kWh — but a single-person apartment uses ~3,000 kWh; an all-electric home with EV charging uses 15,000+.
Where does the CO₂ factor come from?: US EPA eGRID 2022 reports the national average emissions intensity of grid electricity at 0.386 kg CO₂e/kWh. Local grids vary — California is ~0.20; West Virginia is ~0.75. Override the factor with your local utility's number for accurate results.