Green Hydrogen Electrolyzer Sizing Calculator
How big does the electrolyzer need to be, and how much storage? Sized for the hours your renewable actually runs — not the day divided by 24, which is what most tools do and why their answers come out several times too small.
Your power source
This sets the capacity factor, which drives everything
Filled in from your country and source — the share of the year it produces
%
Advanced / Custom Input — the resource
Energy already being spilled. Free input to the electrolyzer.
%
Filled in from your country. Drives the cost per kg.
/kWh
Only used if you are building the generation too. 0 to skip.
/kW
The electrolyzer
They differ by more than efficiency — see the comparison below
Filled in from the technology — use your datasheet figure
kWh/kg
Advanced / Custom Input — the stack
Below this it has to shut down instead of following the renewable.
%
Stacks get less efficient as they age. Applied to the end-of-life figure.
%
Filled in from the technology. Indicative only.
/kW
SOEC only. Without it the SOEC figure rises sharply.
How much hydrogen do you need?
What the off-taker actually consumes
kg/day
A steady off-take against an intermittent supply is what creates the storage need
Advanced / Custom Input — the off-take
Filled in from the pattern above.
h
days
Storage
For cloudy or still days. The daily production gap is always covered.
days
Decides the vessel volume
bar
Advanced / Custom Input — the vessel
Hydrogen is well above ideal at storage pressure. 1.0 would be the ideal gas law.
°C
Added on top of the electrolyzer energy.
kWh/kg
Result
Put in your power source and how much hydrogen you need, then press “Size the plant”.
Estimate only — verify with a qualified engineer or energy consultant and current local regulation before relying on this for compliance or investment decisions.