Polestar Degradation rate converter
µV/h, %/1000 h, mV/kh: one number, every convention.
Method, assumptions and limits
Degradation rates are quoted in three conventions. The first two are the same number: a voltage rise per cell per unit time. The third is relative, and only means something together with its reference voltage.
Reference values
The Clean Hydrogen Partnership lists state-of-the-art 2020 degradation of 0.12 %/1000 h (AEL), 0.19 %/1000 h (PEMEL) and 1.9 %/1000 h (SOEL, at thermoneutral voltage). Reference definitions differ between technologies and sources, so check the reference voltage and operating mode behind any rate before comparing.
Assumptions and limits
- Linear degradation is assumed over the hours entered. Real stacks often show a stabilisation period and may accelerate later.
- The energy effect is DC electrolysis energy per kilogram, before rectifier and balance of plant.
Worked example
0.19 %/1000 h, the Clean Hydrogen Partnership state-of-the-art value for PEM, at a 1.90 V reference.
Input
- Rate
- 0.19 %/1000 h
- Reference
- 1.90 V
Result
- Equivalent
- 3.61 mV/1000 h = 3.61 µV/h
- After 10,000 h
- +36.1 mV, ≈ 0.96 kWh/kg
References
- Clean Hydrogen Partnership, Clean Hydrogen JU SRIA technology KPIs (state-of-the-art degradation values). Source
Engine v0.3.0Last reviewed 27 September 2026 Changelog Report an error
Cite this tool
Polestar Technology (2026). Degradation rate converter. HYDRA engine v0.3.0. https://polestartech.co/tools/degradation-rate-converter/HYDRA Assess: Need degradation as a P10/P50/P90 range for your operating profile? That is HYDRA Assess.