Hydrogen Additionality

Green hydrogen's climate benefit is not automatic: it depends entirely on where the electricity comes from, and the grid does not know your intentions.

Additionality is the principle that green hydrogen production only delivers real emissions reductions if the renewable electricity powering the electrolyzer is newly built and dedicated to that purpose. An electrolyzer plugged into a grid with existing renewable generation does not use "green" electrons. It increases total demand, and the grid's marginal generator, typically natural gas, runs more to cover the gap. Diverting existing renewables to hydrogen production does not reduce emissions. It just moves them.

Tracing what actually happens on the grid. A wind farm already sells all its output to the grid, displacing fossil generation hour by hour. A hydrogen producer connects an electrolyzer and buys certificates claiming that wind power.

Does the electrolyzer actually use low-carbon electricity?

No. The wind farm's output was already displacing gas. The electrolyzer adds new load, and the marginal unit dispatched to meet it is likely a gas peaker. Certificates matched on paper, but the physical electrons were fossil-fired.

Additionality requires the renewable capacity to be new, in the same delivery region, and matched hour by hour, not just annually. The IRA's 45V hydrogen tax credit uses a three-pillar test (additionality, deliverability, temporal matching) precisely because annual or geographic matching allows emissions laundering on paper. Getting the accounting wrong means subsidizing grey hydrogen with green labels.

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