Carbon Intensity of Hydrogen Calculator
The carbon intensity of hydrogen measures how much CO2-equivalent is emitted for every kilogram produced -- and for electrolytic hydrogen, that number is driven almost entirely by the electricity source, not the electrolyzer itself. This calculator multiplies an electrolyzer's specific energy consumption (kWh per kg of H₂) by the carbon intensity of the grid region powering it, using the same EPA eGRID2023 regional emission factors as our Carbon Emissions Calculator, then scales the result to your production volume. The same electrolyzer can produce near-zero-carbon hydrogen on a clean grid or substantial emissions on a coal-heavy one -- which is why genuine green hydrogen depends on the electricity feeding it, not just the equipment. For technology-specific electrolyzer efficiency values, see our Electrolyzer Efficiency Calculator.
Typical alkaline/PEM electrolyzers consume 52-58 kWh/kg -- see the Electrolyzer Efficiency Calculator for technology-specific values.
Same EPA eGRID2023 regional emission factors used on our Carbon Emissions Calculator. Not sure which region applies to you? Look up your exact eGRID subregion using EPA’s Power Profiler tool by ZIP code.
Total kilograms of hydrogen produced over the period you are evaluating.
specific energy consumption × grid region emission factor
carbon intensity × hydrogen production volume
total emissions (kg CO2e) ÷ 1,000
Results update live as you type. For planning and field-check estimates — always verify against applicable standards and equipment ratings.
How we calculate this →Running an electrolyzer on average U.S. grid electricity produces roughly 20 kg of CO2e for every kg of hydrogen made -- often more carbon-intensive than simply buying gray hydrogen made directly from natural gas, which typically runs 9-12 kg CO2e/kg. This is why 'green hydrogen' isn't just about using an electrolyzer -- it's about the carbon intensity of the electricity feeding it. Genuine green hydrogen requires dedicated renewable generation or a sufficiently clean grid, not just any electrolyzer plugged into any outlet.
How the carbon intensity of hydrogen is calculated
This calculator ties the carbon footprint of electrolytic hydrogen to two inputs: how much electricity the electrolyzer consumes per kilogram of hydrogen, and how carbon-intensive that electricity is. Three quantities tie the calculation together.
Carbon Intensity (kg CO2e per kg H₂) = Specific Energy Consumption (kWh/kg H₂) × Grid Region Emission Factor (kg CO2e/kWh). At 55 kWh/kg and the national average factor of 0.370 kg CO2e/kWh, that is 55 × 0.370 = 20.35 kg CO2e per kg of hydrogen. The grid region emission factors are EPA eGRID2023 regional averages -- the same values used on our Carbon Emissions Calculator -- so the two tools share a consistent methodology for converting electricity into emissions.
Total Emissions for Production Volume (kg CO2e) = Carbon Intensity (kg CO2e/kg H₂) × Hydrogen Production Volume (kg). At 20.35 kg CO2e/kg and 1,000 kg of hydrogen, that is 20,350 kg CO2e over the production run. Total Emissions (metric tons CO2e) = Total Emissions for Production Volume (kg CO2e) ÷ 1,000 -- 20.35 metric tons CO2e at the defaults.
The electricity source matters just as much as the electrolyzer itself. The same 55 kWh/kg electrolyzer produces roughly 6.05 kg CO2e/kg on Upstate New York’s largely nuclear-and-hydro grid (0.110 factor) but 23.1 kg CO2e/kg on the Upper Midwest’s coal-heavy grid (0.420 factor) -- a roughly 4x swing from grid region alone. For context, conventional gray hydrogen from natural gas steam methane reforming typically produces 9-12 kg CO2e per kg, so grid-powered electrolysis can actually be more carbon-intensive than gray hydrogen unless the electricity is genuinely low-carbon. Data sources: EPA eGRID2023 regional emission factors; electrolyzer efficiency benchmarks from NREL and DOE; gray hydrogen lifecycle analysis from IEA and industry studies; emerging hydrogen carbon intensity standards from U.S. Treasury, EU, and regional programs.