EV Charging Infrastructure Manufacturing worked example

Contactor Failure Reserve at 1.61% expected contactor failure share: a worked example

What does the result look like when expected contactor failure share reaches 1.61%? The full calculation is worked below with real intermediate numbers. a quality or finance team needs a reserve for contactor-related field failures

The inputs for this scenario

  • Contactors in fielded charger population: 12,000 contactors (unchanged)
  • Cost per contactor failure: 185 $ / failure (unchanged)
  • Expected contactor failure share: 1.61 % (raised for this scenario; the documented default is 1.4)
  • Fixed analysis and containment adders: 9,500 $ (unchanged)

Working through the calculation

  • Applying the documented formula (Expected contactor failure cost = contactor population × cost per failure × expected failure share) to the inputs above produces each figure below.
  • At this operating point the engine returns 45,242 $ for total contactor failure reserve, the number this scenario is built around.
  • At this operating point the engine returns 3.77 $ / contactor for reserve cost per installed contactor.
  • At this operating point the engine returns 35,742 $ for expected contactor failure cost.
  • At this operating point the engine returns 9,500 $ for analysis and containment adders.

How this compares with the baseline

  • Against the tool's baseline example, where expected contactor failure share sits at 1.4% and the headline result is 40,580 $, this scenario comes in 11.49% above the baseline at 45,242 $.
  • A figure at this level is achievable when expected contactor failure share is genuinely sustained, not just peaked for a shift. It assumes a single average failure rate and cost, so it will misstate the reserve if failures cluster in a specific lot, contactor vintage, or duty-cycle population.

Results at a glance

  • Total contactor failure reserve: 45,242 $ (headline result)
  • Reserve cost per installed contactor: 3.77 $ / contactor
  • Expected contactor failure cost: 35,742 $
  • Analysis and containment adders: 9,500 $

Run it with your numbers

  • Every input above is editable in the live Contactor Failure Reserve calculator, which recalculates instantly and can be shared with the inputs intact.

Last reviewed 2026-05-12.