EV Charging Infrastructure Manufacturing worked example

Contactor Failure Reserve at 1.01% expected contactor failure share: a worked example

Suppose expected contactor failure share falls to 1.01%. This page works the full calculation at that level so you can see exactly which result moves and by how much. Estimate a reserve for EV charger contactor failures from installed contactors, failure cost, expected failure share, and fixed service adders.

The inputs for this scenario

  • Contactors in fielded charger population: 12,000 contactors (held at the documented default)
  • Cost per contactor failure: 185 $ / failure (held at the documented default)
  • Expected contactor failure share: 1.01 % (the input this scenario stresses; the baseline uses 1.4)
  • Fixed analysis and containment adders: 9,500 $ (held at the documented default)

Working through the calculation

  • The calculation starts from the formula this tool documents: Expected contactor failure cost = contactor population × cost per failure × expected failure share.
  • Total contactor failure reserve works out to 31,922 $ at these inputs, and this is the headline figure for the scenario.
  • Reserve cost per installed contactor works out to 2.66 $ / contactor at these inputs.
  • Expected contactor failure cost works out to 22,422 $ at these inputs.
  • Analysis and containment adders works out to 9,500 $ at these inputs.

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 21.34% below the baseline at 31,922 $.
  • It computes the expected contactor failure cost across the fielded population and adds fixed analysis and containment cost to produce a total reserve. When the numbers land here, the stressed input is the lever to work; the walkthrough above shows exactly how much each output recovers as it climbs back toward the baseline.

Results at a glance

  • Total contactor failure reserve: 31,922 $ (headline result)
  • Reserve cost per installed contactor: 2.66 $ / contactor
  • Expected contactor failure cost: 22,422 $
  • Analysis and containment adders: 9,500 $

Run it with your numbers

  • To rerun this with your own numbers, open the live Contactor Failure Reserve calculator, set expected contactor failure share to your actual value, and adjust the remaining inputs to match your operation.

Last reviewed 2026-05-12.