How do you calculate first-pass stack assembly yield?

Divide stacks passing first-time by total stacks attempted and multiply by 100. With 232 stacks passing out of 250 attempted, first-pass yield is 92.8%.

What is a good first-pass yield for fuel cell or electrolyzer stacks?

Mature lines target 95% or better on first-pass leak, torque, and voltage. Early ramps often run in the 80s, so the 92.8% here is solid but 2.2 points short of a 95% target.

What does the yield gap to target mean?

It is first-pass yield minus target. Here 92.8% minus 95% equals a 2.2-point gap — the improvement needed to hit the cost model's yield assumption.

Why focus on first-pass rather than final yield?

Rework on a stack risks MEA tears, gasket reseating issues, and catalyst loss, so a stack that needs rework is far more expensive even if it eventually passes. First-pass yield exposes the real process health.

First-pass yield vs. throughput yield — what's the difference?

First-pass yield is single-station; throughput (rolled) yield multiplies pass rates across every station. A 92.8% assembly step combined with other steps gives a lower end-to-end number.

How do I close a 2.2-point yield gap?

Pareto the first-time failures by mode — leak, torque, or voltage — and attack the dominant one. Torque scatter and gasket seating commonly drive leak failures on first stack-up.

Hydrogen Electrolyzer & Fuel Cell Manufacturing calculator

Stack Assembly Yield Calculator

Stack Assembly Yield measures the share of electrolyzer or fuel cell stacks that clear leak, torque, and open-circuit voltage checks on the first attempt, with no rework or re-stacking. It is the single most-watched line metric on a stack assembly cell because every failed stack means tearing down bipolar plates, MEAs, and gaskets — destroying expensive membrane and PGM catalyst in the process. Process engineers and quality leads at electrolyzer and fuel cell gigafactories track first-pass yield daily and compare it to a ramp target to know whether they are converging on commercial cost. The gap-to-target number tells you how far the line is from where the cost model assumes it should be.

What this calculator does

Estimate first-pass stack assembly yield for PEM, alkaline, SOEC, PEMFC, or SOFC stacks by comparing built stacks that pass leak, voltage, and torque checks against the total stacks attempted on the line.
Use it on the daily tier board when stack build cells, MEAs, bipolar plates, gaskets, and end plates have to flow through assembly with a known first-pass rate before warranty exposure builds up.
It computes first-pass stack assembly yield as a percentage and the point gap between that yield and your target.

Formula used

First-pass stack assembly yield = stacks passing first-time ÷ total stacks attempted × 100
Yield gap to target = first-pass yield - target first-pass yield

Inputs explained

Stacks passing first-time leak, torque, and voltage checks:
Total stacks attempted in the same period:
Target first-pass stack assembly yield:

How to use the result

Use it for daily or shift-level line reporting during a stack assembly ramp, or to quantify how far a cell is from its yield commitment.
First-pass yield counts only first-time passes, so it can look low even when final yield after rework is high — pair it with a rework and scrap metric.

Current U.S. benchmarks

Global copper trades at $13,484 per tonne (IMF via FRED, May 2026), up 41.5% in a year, and U.S. industrial electricity averages 8.66 cents per kWh. Both feed electrified-hardware unit economics.

Common questions

How do you calculate first-pass stack assembly yield? Divide stacks passing first-time by total stacks attempted and multiply by 100. With 232 stacks passing out of 250 attempted, first-pass yield is 92.8%.
What is a good first-pass yield for fuel cell or electrolyzer stacks? Mature lines target 95% or better on first-pass leak, torque, and voltage. Early ramps often run in the 80s, so the 92.8% here is solid but 2.2 points short of a 95% target.
What does the yield gap to target mean? It is first-pass yield minus target. Here 92.8% minus 95% equals a 2.2-point gap — the improvement needed to hit the cost model's yield assumption.
Why focus on first-pass rather than final yield? Rework on a stack risks MEA tears, gasket reseating issues, and catalyst loss, so a stack that needs rework is far more expensive even if it eventually passes. First-pass yield exposes the real process health.
First-pass yield vs. throughput yield — what's the difference? First-pass yield is single-station; throughput (rolled) yield multiplies pass rates across every station. A 92.8% assembly step combined with other steps gives a lower end-to-end number.

Last reviewed 2026-05-12.