Green Power Equivalency Calculator - Calculations and References
This page describes the calculations used to convert green power electricity (kilowatt-hours [kWh]) into various types of equivalencies.
Number of American Homes’ Electricity Use for One Year
According to the U.S. Energy Information Administration (EIA), the average annual electricity consumption for an American household in 2023 was 10,260 kWh, an average of 855 kWh per month (EIA 2024). The number of American homes is determined by dividing the annual amount of green power procured in kilowatt-hours (kWh) by 10,260 kWh.
Calculation
The conversion factor for this equivalency statement is [your annual green power purchase in kWh]/[10,260 kWh/American home/year].
Source
- EIA (2024). How much electricity does an American home use?
Wind Turbines Running for One Year
In 2023, the average nameplate capacity of wind turbines installed in the United States was 3.4 megawatts (MW) (DOE 2024a). The average wind capacity factor in the U.S. in 2023 was 33.5 percent (DOE 2024b). Electricity generation from an average wind turbine is determined by multiplying the average nameplate capacity of a wind turbine in the United States (3.4 MW) by the average U.S. wind capacity factor (0.335) and by the number of hours per year (8,760 hours).
Calculation
[3.4 MW average nameplate capacity] x [0.335] x [8,760 hours/year] x [1,000 kWh/MWh] = 9,977,640 kWh generated annually from one wind turbine.
The conversion factor for this equivalency statement is [your annual green power purchase in kWh]/[9,977,640 kWh/average turbine/year].
Sources
- DOE (2024a). Land-Based Wind Market Report: 2024 Edition (pdf) U.S. Department of Energy, Energy Efficiency and Renewable Energy Division.
- DOE (2024b). Land-Based Wind Market Report: 2024 Edition Data File (xlsx) (Capacity Factor in 2023 by COD Year worksheet) U.S. Department of Energy, Energy Efficiency and Renewable Energy Division.
Number of Football Fields of Solar Powered for One Year
The number of American football fields covered with solar panels is determined by dividing the annual amount of green power procured in kilowatt-hours (kWh) by 1,455,726 kWh, which is the estimated annual electricity output of one football field (including end zones) covered by photovoltaic (PV) solar panels.
The factors for this equivalency calculation were determined in consultation with experts at the National Renewable Energy Laboratory (NREL 2023a) using conservative best estimates and utilization of NREL's Annual Technology Baseline (ATB) tool and PVWatts Calculator. Kansas City, MO was selected as the location representative of the “average” solar resource in the US, at 4.99 kWh/m2 per day, Class 5 per NREL 2024 ATB (NREL 2024b).
- Calculate how many kW of panels would cover a football field: 5353.36 m2 * 0.19 * 1 kW/m2 = 1017.14 kW
- 5,353.36 m2 (109.7 m x 48.8 m = area of American football field, including end zones)
- 19% is the assumed “standard” panel efficiency in PVWatts (NREL 2024c)
- 1 kW/m2 is the irradiance value used to calculate a solar panel’s “nameplate” or “rated” power, which is the value used to specify a DC PV system size and is the input to PVWatts
- NREL’s PVWatts calculator calculates that a 1017.14 kW PV system in Kansas City, MO would produce 1,455,726 kWh/Year (NREL 2024c).
- Assumes all other PVWatts default inputs: 20-degree fixed tilt “open rack” system, which is representative of either a large commercial-scale system or a small utility-scale system
Calculation
Note: Due to rounding, performing the calculations given in the equation below may not return the exact results shown.
[5,353.36 m2] x [0.19] x [1 kW/m2] = 1017.14 kW. For the location of Kansas City, MO in NREL’s PVWatts Calculator, enter 1017.14 kW for DC System Size, which yields an estimated annual system output of 1,455,726 kWh generated by one football field covered with solar PV.
The conversion factor for this equivalency statement is [your annual green power purchase in kWh]/[1,455,726 kWh/football field of solar/year].
Sources
- Consultation with experts at the National Renewable Energy Laboratory (NREL 2023a).
- NREL (2024b). 2024 Annual Technology Baseline: Commercial PV. Golden, CO: National Renewable Energy Laboratory. https://atb.nrel.gov/electricity/2024/commercial_pv
- NREL (2024c). PVWatts® Calculator. Golden, CO: National Renewable Energy Laboratory. http://pvwatts.nrel.gov
Miles Driven by an Electric Vehicle
Based upon a review of DOE's fueleconomy.gov (DOE 2024) and conservative best estimates, an average of recorded efficiencies (kWh/100 miles) among fully electric vehicles (Model Year 2000-2024) is determined to be 36.7 kWh/100 miles. The number of miles driven by an electric vehicle is estimated by multiplying the annual amount of green power procured in kilowatt-hours (kWh) by [100 miles/36.7 kWh].
Calculation
The conversion factor for this equivalency statement is [ [your annual green power purchase in kWh]*[100 miles]/[36.7 kWh] ].
Source
- DOE (2024). https://www.fueleconomy.gov/feg/powerSearch.jsp.