Polestar Cell voltage cost
What does a millivolt cost in hydrogen production?
Plant
Method, assumptions and limits
The charge needed to produce one kilogram of hydrogen follows from Faraday's law: two electrons per molecule of H₂.
Q = (1000 / M_H2) · 2F / 3.6×10⁶ [kAh/kg] M_H2 = 2.01588 g/mol, F = 96 485.332 C/mol
= 26.59 kAh/kg at 100% Faradaic efficiency
E_DC = U · Q / η_F [kWh/kg]
E_AC = E_DC / η_rect [kWh/kg]
ΔE per year = ΔU · Q / (η_F · η_rect) · production
Checks built into the tests: 1.481 V gives 39.38 kWh/kg (the higher heating value), and 1.253 V gives 33.32 kWh/kg (the lower heating value).
Assumptions and limits
- The extra voltage is assumed constant across the year. A voltage that grows with degradation belongs in the degradation-rate converter or the LCOH tool.
- Energy is the electrolysis energy only. Balance-of-plant consumption and compression are not included.
- The result is a screening estimate, not an engineering sign-off.
Worked example
A plant producing 10,000 t/yr of hydrogen, with 20 mV of additional cell voltage, 100% Faradaic efficiency, a 97% rectifier and electricity at €70/MWh. These are the values the page loads with.
Inputs
- ΔU
- 20 mV
- Production
- 10,000 t/yr
- η_F / η_rect
- 100% / 97%
- Electricity
- 70 €/MWh
Result
- Per mV
- 0.0274 kWh/kg (AC)
- Extra energy
- ≈ 5,483 MWh/yr
- Extra cost
- ≈ 384,000 €/yr
References
- CODATA 2018 recommended value of the Faraday constant, 96 485.332 12 C/mol (NIST). Source
Engine v0.3.0Last reviewed 27 September 2026 Changelog Report an error
Cite this tool
Polestar Technology (2026). Cell voltage cost. HYDRA engine v0.3.0. https://polestartech.co/tools/cell-voltage-cost/HYDRA Assess: Want to know where your millivolts go, cell by cell? That is HYDRA Assess.