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 2022 was 10,791 kWh, an average of 889 kWh per month (EIA 2023). The number of American homes is determined by dividing the annual amount of green power procured in kilowatt-hours (kWh) by 10,791 kWh.

Calculation

The conversion factor for this equivalency statement is [your annual green power purchase in kWh]/[10,791 kWh/American home/year].

Source

• EIA (2023). How much electricity does an American home use?

Wind Turbines Running for One Year

In 2022, the average nameplate capacity of wind turbines installed in the United States was 3.2 megawatts (MW) (DOE 2023a). The average wind capacity factor in the U.S. in 2022 was 36.2 percent (DOE 2023b). Electricity generation from an average wind turbine is determined by multiplying the average nameplate capacity of a wind turbine in the United States (3.2 MW) by the average U.S. wind capacity factor (0.362) and by the number of hours per year (8,760 hours).

Calculation

[3.2 MW average nameplate capacity] x [0.362] x [8,760 hours/year] x [1,000 kWh/MWh] = 10,147,584 kWh generated annually from one wind turbine.

The conversion factor for this equivalency statement is [your annual green power purchase in kWh]/[10,147,584 kWh/average turbine/year].

Sources

• DOE (2023a). Land-Based Wind Market Report: 2023 Edition (pdf) U.S. Department of Energy, Energy Efficiency and Renewable Energy Division.
• DOE (2023b). Land-Based Wind Market Report: 2023 Edition Data File (xlsx) (Capacity Factor in 2022 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 2023 ATB (NREL 2023b).

1. 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 2023c)
   • 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
2. NREL’s PVWatts calculator calculates that a 1017.14 kW PV system in Kansas City, MO would produce 1,455,726 kWh/Year (NREL 2023c).
   • 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 system output of 1,455,726 kWh/Year 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 (2023b). 2023 Annual Technology Baseline. Golden, CO: National Renewable Energy Laboratory. https://atb.nrel.gov/electricity/2023/commercial_pv
• NREL (2023c). 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 2023) and conservative best estimates, an average of recorded efficiencies (kWh/100 miles) among fully electric vehicles (Model Year 2000-2023) is determined to be 35.7 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/35.7 kWh].

Calculation

The conversion factor for this equivalency statement is [ [your annual green power purchase in kWh]*[100 miles]/[35.7 kWh] ].

Source

• DOE (2023). https://www.fueleconomy.gov/feg/powerSearch.jsp.