Specific Energy Consumption (SEC)

In plain terms

Electrolyzer specific energy consumption is the plant's fuel gauge: how many kilowatt-hours go in for every kilogram of hydrogen that comes out. Lower is better.

The number only means something with its boundary. Stack SEC counts the electricity reaching the cells. System SEC adds the balance of plant: rectifiers, pumps, cooling, gas cleanup and controls. The Clean Hydrogen JU system boundary, for example, runs from AC power and tap water in to hydrogen out at 30 bar and ISO 14687 grade 5 purity.

SEC also rises over the stack's life as cells degrade. DOE defines end of life as a 10 % rise in cell voltage, which means roughly a 10 % rise in SEC.

Typical range

The 4 kWh/kg gap between stack and system in the DOE tables is the balance-of-plant share.

Why it moves LCOH

Electricity cost per kilogram is SEC multiplied by the power price. At the same price, a plant at 55 kWh/kg pays about 8 % more for power than one at 51 kWh/kg. Because electricity is usually the largest LCOH line (IRENA, 2020), that difference flows almost directly into the final cost.

Common mistake