Electrolyzer Sizing Calculator

A less efficient electrolyzer needs more electrical energy input to produce the same amount of hydrogen, since more of that energy is lost as heat rather than converted into hydrogen's chemical energy. That extra electricity requirement translates directly into needing a higher-capacity electrolyzer to deliver it within the same operating window.

The total daily electricity needed to hit a hydrogen production target stays the same regardless of the operating window, but that same total has to be delivered in fewer hours when the system runs less. Squeezing the same energy delivery into a shorter window requires a proportionally higher power rating, which is why electrolyzers paired with intermittent solar or wind generation are typically sized larger than baseload-operated units targeting the same daily output.

No. Electricity price only feeds into the annual electricity cost estimate, not the capacity sizing calculation — a cheap renewable power purchase agreement and an expensive grid rate both require the same size of electrolyzer to hit a given hydrogen production target. Price only changes what running that electrolyzer costs over a year, not how big it needs to be built.

This calculator estimates roughly 9 liters of water per kilogram of hydrogen produced, close to the stoichiometric minimum from splitting water (H2O) into hydrogen and oxygen. Real-world systems typically need somewhat more due to purification and process losses, so treat this as a lower-bound estimate rather than an exact water-demand figure for system design.