Stack life realities vs. brochure claims

Stack lifetime headlines are often optimistic because they assume stable operation, clean inputs, and ideal maintenance. Real plants operate in a different world. Dispatch volatility, supply chain constraints, and staff turnover all influence degradation. If stack life assumptions are not grounded in operating reality, the LCOH model will drift and replacement budgets will be wrong.

What actually drives degradation

Stack degradation is rarely caused by a single factor. It is the cumulative effect of voltage increase, mechanical stress, and contamination. Frequent start-stop cycles introduce thermal stress and water management issues. Operation at low load can increase gas crossover risks, while aggressive ramping can push pressure differentials beyond recommended limits. Water quality and filtration are also critical, especially for PEM systems that are sensitive to impurities.

PEM and alkaline behave differently

PEM stacks are well suited to dynamic operation, but they are not immune to cycling damage. Alkaline systems can deliver long life at steady load, yet they are often less tolerant of rapid changes. That difference matters for hybrid dispatch strategies. If your market plan relies on constant ramping, PEM may be the safer choice, but you still need to cap the number of daily start events.

Operating mode matters more than nameplate hours

Two plants with the same OEM can see different lifetimes based on how they are operated. Hot standby helps reduce start-stop stress but increases parasitic load. Deep turndown can preserve availability but may create efficiency penalties. The best operating mode balances utilisation with stress, and it should be aligned with the dispatch strategy rather than decided in isolation.

Monitor the right health indicators

Performance monitoring is where most plants underinvest. Track cell voltage distribution, hydrogen purity, differential pressure, and temperature gradients. Small shifts in these indicators can predict future degradation. Without a clear baseline, you will not know whether the stack is degrading faster than expected, and you will not be able to justify replacement timing to investors.

Plan spares and replacement realistically

Stack replacements are not just a cost line; they are an operational event with downtime implications. Build a spares plan that includes lead times, storage requirements, and installation resources. Use replacement windows that align with low-demand periods. If you assume replacement in year seven but the supply chain is twelve months, the model must reflect that risk.

Contracting and warranties

Performance guarantees vary widely. Some warranties assume fixed operating profiles or exclude dynamic dispatch. If your commercial plan involves frequent cycling, make sure the warranty aligns. Consider negotiating performance floors or degradation caps that match your expected operating regime. This is one of the most underused levers in LCOH risk management.

Integrate stack life into LCOH

Stack life should not be a single number in the model. Use a replacement schedule tied to operating hours and cycling events. Scenario-test higher degradation rates and evaluate the impact on LCOH, cash flow, and DSCR. This is where the LCOH calculator and sensitivity tools become essential.

Use commissioning data to reset assumptions

The first few months of operation provide the best evidence of how your asset will really behave. Capture baseline voltage curves, purity, and efficiency at multiple loads. Compare that data to OEM assumptions and adjust the replacement plan before the first annual budget cycle. This is a simple, low-cost step that keeps LCOH projections aligned with reality and builds confidence with lenders.

Key takeaways

• Stack life depends on operating mode, not just OEM claims.
• Dynamic dispatch increases stress unless cycling is budgeted.
• Monitoring and spares planning protect both uptime and financeability.
• Warranty terms should match the planned operating regime.